But I am horrified to think that she can't have her own identity except through me. I don't think that's possible or even sustainable. To me this is a huge recipe for disaster.
I agree. That makes you responsible for her happiness and everything else. You are not alone -- not having a clear identity is actually one of the diagnostic criteria for BPD, so many other members are dealing with similar issues. Your wife is the first one I've heard about who has acknowledged it and said it out loud. Nice, though, that she provided some clarity for you!
Not to lay that whole issue on your lap, since it's her issue, but might there be any positive steps that you could take that might help that issue a little bit? Encourage her in her activities, work, hobbies, groups, etc., in a way that helps give her identity and positive feedback from other sources?
Regarding the showers of affection you are receiving, I can totally relate to how hard it can be to accept that affection when it feels like it could go away at any instant. If it helps, those emotions are genuine to your wife when she is feeling them. That affection is real. You know that a black period may be around the corner, but she probably does not. That creates a tough situation. Accepting the affection may be invalidating to you. Rejecting the affection will be invalidating to your wife. Maybe split the difference? What works best for you? I would be curious to hear what other members think.
WW