What she did is unforgivable on such an epic level. Your dreams come first. She should understand that. It's best that you guys broke up. Don't let it get to you. It was for the best.
And dude, she's only your girl friend. You're not married to her. Relax. Focus on your dreams.
I will do my best to reply with an educated, humble and honest answer. Ultimately, it is up to you whether you want to listen to my advice or ignore it completely. Sometimes, my advice may be wrong; occasionally, it will be right. Regardless, I want to do my best to give people answers they are seeking.