well you got a little compitetion, this isnt the worst thing that has ever happend, you need to evaluate these guys game... i mean really break it down, dont just point out there faults also find there strengths aswell. its time to do a little bit of recon reguarding these guys... drop stratigic points about you and this girl hanging out... (DO NOT BRING UP THE KISS) this might through the other guys out of the chase with her but you might also loose her in the process if you seem kiss and tell. do you know how to amog? amog= alpha male other guy... the startigy is clevery delivering back handed compliments to lower social value other the other guy... there is a huge list of ways to do this like interupting him while hes talking to her (basicly makes other guy look inferior to you). or you could mis inturperate something he says to you to make him look like a chode.. *important you need to have girl around for any of these* one i heard tyler durdin using went like this:
other guy: how do you no (girls name)?
Pua: oh her i fucked her

Other guy: oh
girl: him no he didnt hehehehe
pua: shes just being modest

girl: stop it hahahaha
pua: thats not what you were saying the other night

girl: something(interupt)
pua: no her i know her outta class (ie)
this should all be said with a smerk on the face in a funny cocky way..
i have feild tested this one it worked wonders the guy left before i could even look back at him.. and the girl and i were just laughing. granted she was not my target that night but i wanted to see how that line would go so nothing happend between us. (i did end up crashing in my targets bed that night)
now as far as the romantic aspect with the other guys in class for all we know at the current moment there just friends. back when i was really afc i thought a ton of girls were hot didnt mean i was doing jack shit with them. first thing is to not ask jealous of them thats a beta trait what you want to do is just out skill them in game.// this is why the recon is important if you can i want you to actually set up a meeting with these guys like a hang out maybe a study group what eve and get this girl there too she should have no reason for rejecting a social hang out with people that shes already texting and talking to especially since she made out with you.
"pissed off, not at her, but in general, that I thought that she was this sincere genuine girl and GF material, but what she did maybe suggests that she is maybe an attention-whore or manipulative or trying to play the field or whatever"
^I wanted to draw your attention to this this seemed contradictory to me and would come across as jealousy to a girl.. im not saying that your not justified by any means chicks are dumb like that... my wing an i have a saying for them (chicks are like parking spots there whores and liers) you can steal that if you want. but i guess my point on what you have said is that if your to a seperation point with her based on everything you have learned, i wouldnt put in the work...
on the other hand if your not doing anything else girl wise might as well play it out and get some exp maybe learn some new tricks maybe get a lay out of it and who knows maybe a girlfriend if you still want.