I don't know anything about your friend other than what you mentioned here so I'm only expressing my opinion here and nothing more.
I have depression but I'm in better condition now, and speaking from experience, it is generally much easier to fake being fine and happy in front of people I either barely know or don't connect so deeply emotionally. You've gone through a lot with your friend and that is wonderful of you, trust me your friend is grateful of it, but this makes faking happiness difficult which is probably why she's avoiding you. If she's anything like me she might be feeling as if she's constantly troubling you with her 'condition' and burdening you with her troubles, and what you see may just be her way of trying to convince you she's fine.
But again I don't know her so I think the best way for you to find out for sure is asking her.