Wow, that is some scary stuff! You guys sound too young to get married anyway, and man, if you aren't gonna marry her, LEAVE HER!!! Don't be the cherry popper! They turn even more psycho if you take their virginity.
Rule no1: Never be her first. I learned the hard way, and then did it again coz I didn't get it the first time. You will screw this chic up if you sleep with her so you need to make a big decision. She sounds like serious work though and chicks like that make you feel good coz they have to be with you all the time and know you are thinking about them all the time. But that's all about their insecurity, its not LOVE.
If I were you I'd either RUN or if you really like her sit her down and talk about this nonsense. She sounds very immature.