We went from the pinnacle of our "relationship" kissing, making outs, sleeping in the same bed, so affectionate, so much touching, being so open and honest, to her instantly loosing interest in me in like a night, and starting to gain feelings for a guy she just met. All of this in just a week. We never dated, but did dating things, just because she says her feelings for me were strong. She wanted to wait until first year of her college was over.

Tell me why she can have such great feelings for me then suddenly drop them just like that in one night and start gaining interest for another guy all in just a week?

I mean you just don't instantly lose feelings for someone you care about immensely just like that, for someone you hardly know. Yes she is someone who wants to be friends for a long time and get to know you very well before dating happens.