@Fluffytowels24
Team flatmate seem to think it's fine to have a contract with someone and live with someone and then pretend they don't exist. Just because someone is not your best pal doesn't mean you treat them like they aren’t there. That’s not fair, whether friends or not. If you were working with someone you don’t suddenly refuse to acknowledge a team member's existence. If you’re in a shop you wouldn’t just totally blank the shop keeper. These are normal human interactions and there is such a thing as being polite.
Similarly with a flatmate, you still have a relationship that is based on your mutual cooperation over the flat and how you agree mutual areas are maintained and run. If you want no interaction, no cooperation at all, you live on your own. Flatmates need to interact in order to, at a minimum, make sure the flat is ok, communicate about flat issues, repairs, problems, mutual areas, cooperate on bills or communicating over things to do with the tenancy and the landlord.
I don't understand this current trend of ghosting in normal everyday situations. If you need more distance either say so (or write so) or pull back a bit, don’t just refuse to acknowledge someone’s existence.
I see a lot of ghosting as something to do with the internet generation where people see people in real life as though they are interacting through a screen that can be ignored or switched off at whim. But screenlife is not the same as real life interactions.
The complexity here is they were friends due to their anxiety and mental health problems, in which case there might be more going on. Could she be seriously depressed, anxious or mentally unwell? Could there be something else going on back home that she hasn’t told anyone about. She may not even have the words to describe it. It could be that DD is making her feel bad about herself in some way. It could be that she is very down and can’t cope with the kind of conversations her and DD used to have for some reason. The latest you describe about friends and blokes makes her sound a bit competitive with DD, but that could be unfair. Who knows really and you may never know.
In terms of advice, those saying your child is a grownup are very harsh. DD is young and vulnerable due to shunning and bullying in her past and needs more good experiences to build her own resilience and self-esteem. She may be ghosted in other situations in the future, so needs to learn some inner strength and that it’s not her fault.
I’m not sure whether your taking over is the best thing to do. Giving her support to make decisions and take actions herself is more empowering. I would see if DD would like to have some time out at home, which might help her de-stress. Then,with support and care, sit down with her and see if you can draw up a plan of action together. Go through the options (leave, stay, sublet), identify areas that need more research (lease, subletting etc, talking to uni accommodation). Once she’s decided the options and what she wants, you can both draw up action plan.
If L won’t talk, then a letter is probably the only way DD can communicate. Perhaps setting out DD's choice and the process might finally mean L does engage.
If DD decides to stay, she needs to identify the issues that will need communication and how she will tackle this, and have an action plan to stop herself ruminating, by getting out a lot, having a routine, seeing other people, having distracting activities and goals and not expecting L to be the same kind of friend anymore.
Whilst I’m with you in thinking the other person is not behaving well, the best thing you can do is help your DD take the power back and build her confidence. She may feel guilty for abandoning L. But if L won't tell her what's wrong or let her help there's not a lot she can do.
She needs to realise because L is behaving strangely doesn’t mean DD's done anything wrong.