Irena, I'm totally in your guy's shoes (the pivot on a vee-- I've even been the pivot on a dysfunctional vee before!), and I remember hearing/saying a lot of the things that you've written here... I'm also involved with a guy who's rebounding these days, so I feel like I can relate in lots of ways.
Vees can be very challenging, especially when the 'legs' can't or won't communicate. From what you've written, it sounds like your guy has been pretty firm with the other girl about your place in the constellation, and that's something to appreciate and be proud of
; it can be tricky to hear a struggling lover make suggestions/demands and hold your ground. I'd say that as long as he's continuing to take care of you that way, and her issues aren't damaging your relationship with him, then the distance between you and her gives you the luxury of letting her work out her issues at her own pace.
Here's an article from Xeromag that I just discovered on working through relationship issues (not sure how I've been missing it all these years). For me it gave a nice, neat metaphor for thinking about situations I've been in; I can see the forest AND the trees now! I've passed it through my constellation for exactly that reason, and it might do you all some good too:
(Maybe he could pass it to her, pretend you hadn't seen it?
Good luck, in any case, and thanks for sharing your story!