I think it is hard to know what your friend is thinking. Her behavior is evasive, so even if you ask directly, you are not guaranteed to get a straight answer. I agree with you that her change in signature is probably significant, even though it's a small thing.

I try to interpret these kinds of situations as matter of factly as I can. For whatever reason, friend X isn't contacting me or responding anymore. For a very good friend, I do still keep in touch periodically, with a call/email/txt every few months or so, even if I don't get a response. If I were in your shoes, I would simply accept that my relationship with this person has changed (even if I don't like it). It really does suck when people you like a lot don't want to be as close anymore.

I have noticed that deaths can completely change a person's life. My neighbor's husband died a few months ago. Ever since then, her house is always full of people I've never seen before. For years we would go to parties at this woman's house and the only people there were neighbors -- now I never see her because there's always a crowd of strangers. At first I thought that these people would drift off again, but it seems like the funeral let her renew old relationships.