it's obvious you really care for her but i think you're trying too hard to fix her. i think it's better to back off a bit and let her come around in her own time. you might want to do some reading on co-dependency and learning to keep the focus more on yourself. you just can't change people no matter how much you want to help. it would be better to accept her how she is--negative thinking and all--or find someone else. she may eventually end up resenting you if you keep trying to "help" her because it can quickly cease to feel like help and end up feeling more like you're being controlled and harassed. sorry, i know that probably isn't what you want to hear.