Once a cheater... always a cheater.
You're only fooling yourself. By forgiving her now she knows she can get away with it.
I'm afraid he's right. She has already set the discourse her way. She probably knows that you are tied to her emotionally and she enjoy's torturing you in a big way. NEVER get tied to any woman alive, no matter who she is.
If I was you, the best way to get over her is to bed someone else. Find a babe, show her the best time and by the way, make sure that horrible 'creature' finds out in a subtle way that she's been replaced/forgotten. Trust me, they HATE that more than anything receiving the same treatment they dish out.
One final note for you (because no one has the guts to mention it yet), because your 'Girlfriend' seems to love having sexual relations with others (strangers on Campus or Off) how do you know that she is clean? Meaning, can you be 100% sure she hasn't contracted any STD
or the monster in the room, HIV?
Make sure you are protected FIRST before anything else. I know here in Australia HIV is fully covered under our health system but can you say the same for yourself?
If you haven't used a condom before maybe it's time to buy several boxes of heavy-duty
Durex/Trojans right now.....