Partner's teenage DD making life hell

[footieandfood]

I'll preface this by saying I'm a guy, looking for advice.
Partner and I have been together 5 years, got engaged after 2 years. We live separately but see each other several times a week. I stay over at hers and vice versa, subject to our work shifts.
My partner has 2 daughters and 2 sons, the eldest DD (almost 20) is absolutely lovely, very kind, warm-hearted and respectful. The DS are both living away from home so I don't see them often but when I do, we get on well and they've always been respectful.
The youngest DD aged 14 is another story. She's been rude and spiteful to me ever since I appeared "on the scene". Tells me (in front of her mum) that she hopes I get dumped, wishes me dead and that her mum doesn't really love me.. Of course I know that's nonsense but it's still not nice to hear on repeat.
She's spiteful to her mum too, screams at her to f* off. There's been a pattern of her refusing to attend school over the last year. Mum has checked with school and friends etc, no issues like bullying or struggles with the work. The DD is extremely bright, excels (when at school) and gets good marks.
During the summer we went away for a week and this DD kept trying to get into our bedroom (locked for privacy) at night. When she couldn't get in, she would hang around outside the bedroom room and scratched the door with her nails, making stupid animal noises.
No diagnosis of anything medically wrong with her and no neuro-diversity diagnosis.
I'm at a loss to understand her behavior and it's putting a strain of the relationship. Her mum lets her swear and scream at her, no boundaries etc in place. Obviously it upsets me to see/hear my partner being treated in such a way by a 14 year old child.
Any advice?

Why?

OP please Google NVR it stands for Non Violent Resistance and its a different type of programme for parents with young people displaying the same behaviour as you describe. I work for a local authority in London and one of my tasks is to facilitate this programme with three other people. We have run 12 programmes now with good results. One if the biggest fears parents have is challenging the behaviour causes escalation. Children and young people are often unable to regulate their emotions for whatever reason and need a parent to help them with this. Wish you all well

"Not answering back" 🤣🤣🤣. Her daughter is the child and she is the adult. She needs to take back more control and have boundaries. Personally I would cut my losses, getting involved with someone with 4 children and 1 of them is feral sounds like a nightmare. Life is too short for these complications and hassle. Your fiancée is being walked all over

No!. Her mother has the right to have some privacy!. Children need to understand their parents are human beings too. Not everything can revolve around them. if there is no emergency, there is no reason she needs to access her mother in the middle of the night.

Your Partner has to put her DD first and if you want to continue the relationship you need to support her in this by backing off. I’m appalled that you and your partner felt it was appropriate for you to join the holiday. I agree with all the posters who say that DD needs emotional care and support from her parents. Shame on the Father who’s effectively abandoned her. She may be ND but emotional support needs to be addressed.

It sounds like Your describing autism
I am diagnosed with it and my children are ,mine make animal noises.
Mine would be very distressed being in the situation your partners daughter is

I see that you missed out on therapy as well then...... how ridiculous!

Got to say this is the weirdest thing I have read on here in a while!

I don't think I would be impressed with a 14 year old scratching on my door and making weird noises, just a thought but if she was asleep she wouldn't know the door was locked.
Mum's are allowed privacy too, perhaps if she is being intimate with her partner she thinks locking the door is the responsible thing to do.

A mother is a person, not a household appliance.

What do her older siblings think?

My daughter was similar at that age. It is jealousy of you getting her mums attention and her feeling shut out by her mum. She’s feeling very insecure and frightened of you taking her mum away from her. Probably worth backing off a bit and spending less time around her mum when dd14 is there. This may be necessary for the next two to three years. Letting her see her relationship with her mum is secure will help.

What on earth is wrong with you? incredibly disturbing, would you do this to your adult children?
Why is everyone pandering to a 13 year old behaving really badly?
her mum has been with a man for 5 years and she has not moved him in. The dad fucks off so the mum can’t ever have an adult relationship?
madness

Absolutely agree
one of the most important things to teach children is the world does not revolve around them.

Erm……ok.

Don't be so literal!

My advice - run for the hills.

What a gross comment, do you struggle with social interaction?

There is something going on - PDA/ODD? This is extreme behaviour.

Orpheya
If my mum locker herself at night with no matter who , I would bloody kick the door down. And I am not even a teen but a old 50 year old

I take the view that if my mum wanted to lock her bedroom door when she is on holiday, she can as she has capacity to do what she wants.

I know you probably ( hopefully) mean this figuratively but Why would you 'bloody kick tbe door down' Bonkers!

The girl is 14. A child, she has every right to access her dm when needed.

Absolutely not, unless tbe child has a
serious medical condition that needs 24hr support, mums ( and partners) have the right to privacy. The child isnt a baby or a toddler and if they need something urgent in the middle of the night they can knock and wait. That is showing respect to others.

This fella isnt a fly by night, he has been around for 5 years. Mother is entitled to a relationship and I agree with others it is a Dp problem and dd needs to be told that the boyfriend is here to stay and start putting in consequences for bad behaviour.

Ive worked with kids that have done the strange animal noise, not at home but in classroom. When I unpicked the last one that did it, it was because she 'hated' the teacher and wanted to 'mess with her head'. This child is not ND. She just got on all fours in the middle of a lesson and howled.
Unfortunately for her, it got her a suspension but also her peers still take the piss out of her and not in a light hearted way.