Not only have I read this thread, I've read at least three threads on the subject from this OP.
She is apparently reliant on someone cooking her evening meal and caring for her dog.
She bought a dog when she lived in shared accommodation (not a great choice IMO) that she had to leave, before the end of her tenancy because she didn't get on with her housemates. She drops her dog round to her mum's for some dog sitting when she is at work.
She's not reliant on anybody cooking her evening meals - she has lived independently at uni and in her houseshare before. The OP does that as something nice to do and to spend time with her.
She becomes distressed when her mother leaves her home alone.
She 'becomes distressed' when her mother leaves having visited for an hour. She is abusive towards her mother if she stays longer; in fact she is abusive towards her whole family on and off, as well as towards others who she has lived with - which is why she's living by herself now. She used to behave so badly when she lived with her mum and stepdad that her much younger siblings would avoid her. I don't disagree that she likely has issues, and would undoubtedly benefit from seeing if she needs a diagnosis from relevant professionals, but I don't think this automatically means that she is vulnerable. She could also just be a 20 year old who needs to get a grip and stop acting out.
Apparently she has been on Onlyfans - when know that young ladies are drawn into this sometimes when they lack support.
If you haven't read previous threads you may have missed that her mum has repeatedly tried everything she can to get her to stop going on OF. DD has not been on there through lack of other options, nor through lack of support to leave it, she's been determined that she's going to make a ton of money and find her fame doing cam girl work, and had been totally uninterested in the reality (that she's earning a pittance) and the other consequences that DM has repeatedly tried getting into her head about it all. She's been doing camgirl work in the house and walking around in lingere with her 7 year old sister around. She refused to get a Xmas temp job to save money up for a rent deposit on the assumption that her mum will eventually cave and pay it - mum paid the remaining months rent on her previous tenancy when she moved back in too.
It's great progress that she has another job now, but I anticipate that she'll be walking out of it any day now.
She's had therapy paid for, for years. On top of an awful lot of other support.
So - not functioning very well in any of her relationships and possibly has a personality disorder or mental health condition not yet diagnosed, yes. Vulnerable - I'm not convinced.