How do I stop my step daughter

She's old enough to have consciously made the choice to call you that. I understand your reasoning behind being nervous of her calling you mum but it is odviously important to her. I would though question if there are problems with her and her biological mum which may have triggered this so maybe take her out and have a bit of a chat to see if there are. Let her know your reasoning behind why you said that and that it is not a rejection. It sounds like she views you as her mum and that goes far beyond being genetically related. But if she really wants too I wouldn't stop her personally - it sounds like you've done a great job and she loves you for it.

Speaking from someone who took in their teen stepdaughter a few months ago due to a breakdown in relationship with their mum, I would say to her that you are flattered she feels that way but please could she make sure her mum doesn't overhear etc as you don't want them facing any backlash. That way they won't see it as wrong but they know the reasoning to be careful with their wording. If god forbid their relationship breaks down further you may be who they lean on for comfort and to feel safe within a family unit.

I have a very dear friend whose SD calls her mum and it started when SD was about 13 and the relationship with her bio mum was going south. The SD is now 28. It started when she was in group situations and didn't like saying Step Mum as people then often asked about her family set up which she didn't want to explain. I've no idea if her bio mum ever found out, but SD moved in with her dad permanently at 15. I'd take it as a sign she really loves and respects you. She's 14 please don't discourage her - just go with the flow if you can.

She is calling you mum because she is having a fell down with her mother. She may be doing as a sign of appreciation or as a sign of anger towards her mum.
Either is tricky I wouldn't correct her because both your you knows there is a mum and a step mum. She may revert the calling or carry on with it, in any case don't make a big deal of it. Just support her as you have been doing all this years.

I agree with PP that it is a sign of love and security.
Can you make a cute name that's not mum, that she can call you, make something up together, like a secret code for all the mum love and things, but not actually the word Mum. It sounds like she wants a word that is not just your name, that signifies that family bomd and closeness, like Mum or other family names (dad, aunty etc) mean a lot and takes the coldness out of a formal name.
Not aure what it could be but yoh cohld think of things together. Or mum in another language even.

If she's not getting along with her mum then I'm guessing that calling you mum is a middle finger up to her own mum, even if it's behind her back.

You sound amazing @Janespotatoes.

As above I'd try not to discourage or encourage. Just let her do her thing. She's old enough to understand the ramifications.

She clearly sees you as the mum figure amd for whatever reason needs to have that mum connection.

My dsd called me mum for a bit when dd was little, dsd would have been about 10. She probably did it for about 2 years and then stopped and went back to ihatelittlefriend. Again, it was during a time when her dm was focusing heavily on her own dsc and was ignoring dsd's needs a lot. Dsd felt quite out of place at her dms and because I have always maintained that we didn't operate a 2 tier household, his kids and our shared dd were all treated thr same (age appropriately obviously) she always knew where she stood with me. Once things calmed down with her dm she stopped calling me mum. She slips every so often now, but she is nearly 20, at university and her dad and I split 8 years ago. But we are still very close.

Aw it’s lovely that she can tell you how much she appreciates you. Maybe it’s a good opportunity for you to say in return that you are honoured / see her as a daughter / will always be there for her.
Sometimes in life we don’t get round to expressing our love properly, so it’s fab that you and she can!
You could also then gently explain that you think her mum would be upset to hear her say it, and that you don’t want to tread on mum’s toes or cause upset.

How about she calls you Mumtoo or something similar? Obviously, you are both very fond of each other and you care that she doesn't stir up trouble with her bio mum so there is a middle ground to be found.

You've been in her life since forever and she's chosen to call you mum it's not as if you and your other half have forced her to call you mum. If her bio mum does hear it she should be happy that you've shown her daughter enough love that she's happy to have you as a mother figure in her life. Does your step daughter live with her mum or is she living with you and her dad?

My kids call me mom, and their step-mum they call her mum.
And I couldn't be happier it means that when they're with their Dad they're clearly happy that she spends time with them!

She's 14 and she's old enough to decide whether she sees you as a mum or not. If her birth mother is furious, that's a conversation between her and her daughter, but I think there are plenty of stepkids who have step-parents in their lives for so many years that they see themselves as just having two mums/two dads. I know at least one adult who calls both her biological dad and her stepdad 'Dad'.

My son calls my DH his stepdad by his name but I have noticed when we are on holiday or in group situations he always refers to him as my Dad. He does have a dad too. When I asked about it he says it's just easier.

Why has the relationship with her biological mum gone downhill? Is it because of normal teen stuff? Like in the way that a normal parent teenage relationship can be a bit strained? Or is it because her mum is a shit parent, has let her down, is emotionally abusive or similar?

If it’s the former then this might be a form of playing one parent figure against the further. You and OH need to gently unpick this with her and remind her that her mum loves her and is trying her best and really it’s not a good idea that she call you mum, much as you appreciate it and enjoy being a mother figure to her.

If it’s the latter I would probably let her. At 14 she is old enough to know to avoid calling you mum in front of her and it’s great she loves and trusts you enough to cast you in that role. Ultimately her mother will reap what she sows in terms of a relationship with her daughter. And if she does get wind of her calling you mum, just don’t enter into any arguments with her. Ignore, block and leave any and all communication to your OH.

Just keep gently correcting her

Why has her relationship with her mum gone downhill? Is it a clash of personalities with a mix of teenage hormones and general growing up/pushing boundaries?

You don't say what she's like generally. At 14 is she trying to get more freedoms than mum will allow? I'm wondering if mum is having to be the strict parent. Could it be she's trying to sweeten you up with a view to proposing she live with her dad and you in the hope you'll be more relaxed with rules? Just speculating here.

I'd take it as a sign that she loves you and trusts you. Please don't reject that.

At 14 she knows the difference between you and her mum. Let her decide what feels the right name for you. It's her choice not her biological mum's. She's not a confused toddler that needs the difference explained.

She might keep with it but she might change what she calls you as she gets older. 14 is such a tricky age. Don't cause issues when really there are none. Welcome her sign of affection.

You can have more than one mum it’s not just biology. It’s testament to the relationship she has to call you that and I think it’s lovely. I wouldn’t discourage it - her biological mums jealousy should not cloud what you have. What about if she married and has a super relationship with her mil? I called my mil Mum as that’s what she was to me. Didn’t mean I didn’t love my other mum too.

Be careful about this. I know you're trying to protect her from fallout, but it'd be very easy for her to misinterpret your reasons and feel hurt or rejected by this. Almost as if you only 'accept' her in private, especially if you have biological children too.

You mentioned that you have biological children. Is she joining in with them to feel more a part of your family?
I would let her do it, believe me she knows what she is doing. Take it as the compliment it is. My Dad has been married to my SM for 38 years and there is no way in hell I would ever refer to her as my mum!

At 14 I think it's up to her.
You all know you are not her Mum.

I wouldn't correct her any more. You have already and she has continued so she is making her choices. It may be that she is doing it only to get back at her mum but more likely she is feeling a bit let down by her mum and is trying out using it as a safe and loving word with you too, to feel closer.

I'd view it as an honour and treat her accordingly. Telling her 'don't call me that' might sound to her like you don't view her as a daughter. From the sound of it that's not the case and might make her feel rejected and foolish. You don't want to take that risk.

Sounds like you have a lovely family btw OP, you're lucky to have each other.

Is there any special alternative she could call you like "bonus mum" (but that's a bit twee).

There's a Jewish word 'mishbucha' which means related in a complicated way. A personal variation of something like that could be sweet.

I would probably let her carry on tbh! Otherwise she might feel a bit rejected.

It wouldn’t have been good if you’d asked her to call you Mum, but as she’s done it of her own accord, I would let her continue.

I come from the pov of not having any children, but my kids having a step-mum. I wouldn’t be thrilled if my kids called their step-mum “Mum” but if they did I wouldn’t be getting cross with anyone or saying anything as it would obviously be what they needed to do.

But I hope my kids are very emotionally comfortable and secure with me, which doesn’t seem to be the case with your DSD and her Mum.

My dd(16) wishes their step-mum happy Mother’s Day and that doesn’t bother me.

That’s what I wondered. Is it maybe to hurt her mum?