When someone says "I'll wait for you"

^ | Probably the best Idea xD

Frankly, she sounds highly immature. If she's around your same age, it doesn't honestly surprise me. It's purely a crush, but an unhealthy one. If it bugs you that much or she goes to far in trying to spend time with your or hurt your relationship with your current gf in any way, then some tough love would probably be in order. Tell her flat out you're not interested and won't ever be and cut off all contact. This is the kind of shit that can start bordering on obsession/stalker like behavior and why I'd be pretty wary of such a person.

The best course of action here is to Inform this person that you don't see yourself developing a relationship of that kind with them. If you value them as a friend than you should make that know. There is nothing worse than leading a person on and giving them the false hope of something happening when there clearly wont be. I someone says they will wait for you and or i can live without you, most take it with a grain of salt. However that being said depending on the persons emotional and mental state it could turn into an obsession if not handled bluntly. As we all know obsession can lead to stalking which inevitable leads to a Murder-suicide kinda scenario. But most of this can be mended by being straight forward and honest. Also if the situation has been handled feel free to ignore this post or if you are going through something similar, just remember though i may be hard it is better to be direct than give the other person the illusion of being in a relationship with you.