To believe sis(12) over SD(11)?

@Bestofgoodluck at least you’ve got to the bottom of it , this child obviously requires some help so perhaps it would be best if she goes to her granny in future as really you have no idea if these things were said and if they were why did she not come to you at the time .

Because she knows these girls
Their personalities.
What they're like.
Behaviour is often predictable.

Given your update, it’s very clear that DSD father needs to do a hell of a lot more.

You need to protect your sister from the fallout and keep some distance whilst the situation is resolved. If you were my DD (she’s a year older than you) I would be very concerned about the situation you find yourself in. I would be encouraging you to stop staying at your boyfriends house when he isn’t there, it’s not fair on anyone.

Why do you belive you're entitled to this?
OP is clearly reading the thread so why did you not get the hint that she isn't answering after the first post let alone the second?

You are doing so much OP to prop up the poor parenting exhibited by everyone else around you. Your DS clearly needs you and your DSD must be very insecure over her caregivers (understandably) to have tried to oust your DS and keep your attention on her.

I think your DP needs to very seriously consider changing job so he can be around all the time. Your DSD desperately needs stability and this is his responsibility. This leaves you able to give your DS full attention when she needs it. Do you think she is likely to want to move in with you full time at any point?

It sounds like SD has wound herself up into doing something silly, then backed off when the option was that she goes to grandparents, i.e. she doesn't win all your attention. I wonder if your sister gets a bit jealous too? Both girls could use some family time to work out how best to be kind to each other.

As the DSD is in your care and clearly troubled about something I'd focus on giving her a big hug, tell her that you care about her, and that you would prefer for her to always be honest with you but will still care about her even when she isn't. I would tell her you're sorry she has clearly got upset about a lot of things, and you'll help as much as you can to help her to feel safe and happy again. Ask that she tries to understand that life is not easy for sister either, so it may be best to work through issues together to see if they can be more supportive and kind to each other. The time to get into why it was wrong to lie about DS messages isn't now when she only has you and knows you have to choose DS and send her away to grandparents if the conversation goes badly, her situation is too vulnerable. Be led by her about whether she wants to talk more now about this or any more urgent issues at school, or wait for dad.

Ok, so SD says she sent the messages herself because your sister actually said those things to her. Sister isn't completely innocent then IF she did say disgusting things to SD. You've said yourself she can say some really mean things.

11 and 12 year old girls can be horrible. I've been there. You need to iron out any bitchiness between them. I think the best solution if you are staying with DP is that SD goes to grandparents when DP is away and your sister stays at you place with you when she needs time away from home.

Although I also think your DP needs to seriously think about spending so much time away when he is a single dad. SD is entering a really crucial stage of development and the transition to senior school can be hellish if they get mixed up with the wrong kind of friends, hormones raging and already coming from a broken home.

What a thoroughly nasty take on the situation - from someone who does not know any of the people personally!!

I think some posters on here are assuming a lot... Based on the limited info OP has given her DP isn't making her look after SD, and has also been trying to help from a distance with this issue.

OP also sounds like she is very responsible and has been from a young age.

speaking bluntly. Your DP has manipulated you into acting as an unpaid nanny with benefits. Your SD has attempted to manipulate you into getting rid of your own sister. The apple didn't fall far from the tree. You should take your sister and get the hell out of there. You both deserve better.

Its a bit confusing

My thoughts too.

Well it is good she's admitted it, but is she STILL saying that your sister did say these things, even though not in text form?

Obviously it's crap it's meant your sister could have got in trouble but I feel a bit sorry for you SD that she said such nasty things about herself

I guess due to her age she might not totally know exactly why she sent them. But obviously some deeper emotional things going on - whether it's really about your DSis or something else.

Could be a cry for attention because bigger issues (bullying? Insecurity?) or again feeling threatened/jealous of relationship with DSis.

So she has said it was her?

I was wondering if the girls had a falling out earlier in the evening. Did you see a lot of them in the evening?

Yes it does sound like a cry for help from SD.

Feeling that you don't believe someone's version of events based on what they have told you is not prioritising other people above that person.

The OP has clearly given her the 'benefit of the doubt'. She already said she cannot be sure and she feels uncomfortable accusing either of the girls. She has also provided a solution so that the SD doesn't have to be around the sister.

Honestly, who cares what her partner thinks right now, he isn't there. If he feels his child is being treated unfairly then he is free to do the job himself. Also, he would be completely mental for dumping the OP simply because she didn't instantly believe every word his 11 year old daughter said.

Perhaps five days was just too long.

I hate men like this. Playing on other people's kindness (and traumas). Can just imagine him "bonding" over how they became solely responsible for young children through no fault of their own. Fast forward 5 years, he's carrying on with his life because the OP has taken on the responsibility of another child. It's no wonder he's not taking his daughter's side here. He doesn't want to lose this setup. It works for him, that's all that matter.

Well yes you are right there. OP will soon find out if she only has value if she continues as a Nanny with a Fanny.

Exactly my thoughts…

@Lyraloo I think you need to read the OP again. The answers to your questions about why the sister is a vulnerable child who the OP has always needed to care for since she was born are provided there.