I am sorry to hear how she has reacted...I kind of have been in the same position, not as long and not as close, but similar in the break up part. He said he liked me more than I know, I'm a great friend, good person, he thought our time together was 'incredible' (his word, a favorite)...but first he said he needed to be by himself and second he said he missed me but couldn't give me what I wanted. So, I understand the hurt and confusion.
I hope she comes back, it sounds like things were really good.
I don't know if my guy had mental illness but I suspect Asergers' syndrome. So I probably overwhelmed him with my anxiety issues...I was not having any mood problems thank goodness.
You'll be in my thoughts, I wish you the best.