Should I prepare myself for another round of the usual splitting until she can get through this current difficulty?
this may be taking things a little bit lightly.
reread your post.
you detail significant, ongoing, mental health crises in your loved one (loss of her best friend, hospitalization, loss of memory). i dont know if this is the usual splitting, i dont know if she will simply get through it, and im not sure its the most supportive stance in terms of rehabilitating your relationship.
things are tumultuous...they are, more than likely, going to remain tumultuous. its not clear what sort of support or help shes getting, if any, upon leaving the hospital. while she needs it, its also not clear she will be getting it. while all of this is above your pay grade, so to speak, the most likely indicator of a loved one with bpd recovering is a strong and consistent support system.
the question(s) id be asking is what does that entail for me. what is it going to take, how much can i reasonably give, what are reasonable expectations for her outlook on recovery, let alone for our relationship, in the short term and the long term.