My girlfriend thinks she is ugly :( Help?! She is always talking about how there is way more beautiful girls!?

I love her with all my heart she is the most beautiful girl in the world to me! But the problem is she is not confident enough about herself because other people say she is ugly! :( help? I love her but I can't have her pitting herself down... She also was gonna cut and be emo at one time because of her life and she hated her life and just a few days ago she told me she hates her life and she just won't listen and agree with me when I tell her she is beautiful..... She takes things too seriously but I still love her! :) help please! Thanks