I understand. I'm in the same place too. I just don't trust myself to be with someone and I don't trust the person. Right now, it's not worth taking the risk of falling into depression for the 3rd time. Is that how you feel?
You sound very insightful and that's a good thing. You are able to identify what you need to do in order to look out for yourself.

You shouldn't apologize, you were venting and expressing what you feel. It's part of the process. It's how she made you feel. I think that you can still care about her overall but that can be separate from the outcome of your relationship with her. I know my ex, who has addictions, was selfish and treated me like crap towards the end. But! I still want him to be ok, I'm pissed he didn't like me. But, when someone has issues like that whether addictions or emotional problems it's best to let them be. Maybe, in the future when you no longer have these feelings about her you can check to see if she's ok. But you have to make sure that if you do that and there's communication that you're strong enough, indifferent enough about her to not get pulled into her vortex.