Look inside yourself. Equality in relationships i don't think is a valid goal. A better goal is balance in the total relationship. If you can't get over your girlfriend's salary being higher it's likely you think less of yourself in other ways. That's possibly why you can't deal with the salary difference, not knowingly, but most likely. If you can't figure it out and change, get some counseling. It can help.
girlfriends salary? U can learn from her . See what she has that u don't have , education wise, skill wise and behavior wise.