"really loves"--? yeah, sure. for a freshman and a sophmore in college, it feels like that. when you're 30 yrs old someday you'll look back and see "first intense relationship one step up from a serious crush."
but, like, (porky pig voice here) weally twue wuv?
doubt it.
you can try the AFC route, and it may work, too. it'll take some time and a lot of effort and you'll get the drama anyway. i've noticed this method appeals to those who want to avoid a confrontation. it's for those not ready to step up, take responsibility and define for themselves how their life will be conducted.
when you make it crystal clear to yourself what you are about, what you're doing and how you want to live, you can then lay it out there to other people in your life without apology.
i'd suggest being straight up and level. don't make it a long, involved explanation, don't apologize, don't make it heavy --- just keep it level and simple and state "i am 19 yrs old and nowhere near ready for marriage at this time and probably won't be until i'm at least 25. i like being with you, but talk of marriage is getting way too heavy and ahead of things right now."
if she argues or gets manipulative, just keep repeating the above
funny - isn't it? - how you're doing a job on yourself with the "i'm afraid to break up with her because she might commit suicide." if that's the way things really are, you're in a sick relationship and should get out.
try the direct straight-up approach; it's faster, better for you and won't take as much out of you. who knows, maybe she can deal with honesty better than games and manipulation.