sounds very similar to me at 17. mum hated my boyfriend and his family based on nothing but what she had heard from other people.
tbh her big mistake was letting me know she didn't like him, the relationship, his family etc. the more she objected and tried to restrict my time with him, the longer I stayed out, the less contact I made with her, the less she knew, the more she worried.
my advice would be to let this run it's course. let her work though whatever she needs to work through. let her know you and dad are there for her but (and I am a parent now- I know how hard this is) try and relax, at least outwardly, about this as it is most likely just a phase she needs to work out of her system. don't give her a reaction if you think that is what she is after. continue your relationship with her as you did before 'the change', if you two used to go for lunch then still go for lunch and chat, let her direct the conversation. if she wants to talk about him or her ex or anything then listen and let her say what she needs to say. one thing my mum still finds very hard is to just listen when I need to talk- she cannot switch of the 'lecture' mode and realise that as an adult, what I decide has to be my decision and not her instructions. it has made it so that at 27 years of age I cannot recall once ever just having a chat with my mum. I just cant talk to her at all now beyond what the weather is doing.
I know it is hard- I was no model teen but I think my mum handled it badly and was partly to blame for the way our relationship went. if I could go back in time and advise her I would tell her to back off and relax, if even just infront of me, and let me get back to being me in my own time. 17 is a tough time.
I would also say that DD needs to keep to the house rules that already existed before this started. don't introduce new ones though just to 'punish' her or to restrict her freedom because you cant cope with her having so much.