I feel for you, I've been on both sides of that situation. Think back to your depressive times and see if you remember giving yourself similar negative self talk. I know my ex H was not able to understand my depressive times at all, it made him angry and frustrated...really not the best way to make me feel any better. More recently, I had a boyfriend who had lots of mental issues, inadequately treated in my opinion, however, it took a toll on me and caused my own issues to rear up despite adequate treatment.
It would be my suggestion that she needs to go back on some kind of antidepressant because her behaviors certainly indicate she is in a depressive state...and what ever methods of coping with your own issues would be a good idea to use as well for yourself.

I don't think she is bringing up the past incidents to make you feel bad, I think she feels bad and the memories that are coming up are the negative ones...I know I would end up not thinking about good times when I was depressed, the negative things were always up front. It's part of the package. I do realize that in the literature, men sometimes experience depression in a different way than women. Not always obviously, but sometimes.
Take care of yourself and encourage her to see her dr and be very honest with how she is feeling/thinking...esp with the self harm. that is a really difficult thing for a partner to witness I think you did right in leaving at that particular time.
I wish you the best