My personal take on the matter is:
She's having a serious problem, and can not or does not want to discuss it with you, while you're the only qualified person for it. Perhaps she's afraid of contact with you in fear of confronting her problem.
I'd go with the advice given above: ask her outright (not bluntly ofcourse).
If my scenario is true I hope she's honest (even if she doesn't want to discuss it right away) and your friendship could get a good new beginning.
If she 'turns you down' then walk away. There's no telling how pursuing would turn out. If you really care for her be available, don't push it, but don't depend on it either.
I acted like her once and shoved my best friend away. In all honesty I needed him most at that time... Luckily he took it well, gave me my time and on the very first occassion afterwards I thanked him a lot for it. It gave our friendship an even better basis than before. But I'll be damned if I ever pull that shit again.. it hurts people
So got a load of my chest here too
EDIT: serious typo corrected.