Hi @Hopefulhorizons i wish i had a parent as loving as you.. i can speak from your daughters prospective because i have the same diagnosis,, the behaviour you just described is exactly how i existed for almost 3 years, not that long ago..
I will tell you how it was for me Because i dont want to assume something that's wrong and upset you or stress you more than you are..
My bedroom was my safe space away from the harshness of people at work and the demand and responsibility of my work, i didn't even answer my phone if i was watching my show in bed. I felt safe and it was predictable for me there was no anxiety that someone needed something from me or i forgot to do something or i had a deadline/appointment/meetings/shopping there was no pressure. But i was so miserable and lonely because i didn't know how else to deal with myself and besides work and overworking all the time, i had no purpose to drive me to do anything other than stay in my room and watch my show.
My partner was in prison so besides phone calls and an hr a week visit, it was just another chore before i went back to bed.
For me isolating has always been my escape either for safety, depressive episodes, bordem, anxiety overwhelm, fear, avoiding something, predictability and sometimes for attention.. yep i said attention, and procrastinating.
Talk to your daughter.. its likely she might not know why because of the ADHD or maybe she does but doesn't know how to handle it so thinks she is handling it, thats the BPD.
If shes medicated for her conditions then maybe she needs a med review or change.
Definitely she needs a lot of B vitamins b1, b12, b2 etc they make a huge difference for ADHD symptoms.
I hope things work out for you and your daughter. She will find her light again, she has you watching out for her.