A lot of the time (certainly not ALL the time, and probably not even MOST of the time), a woman is bitchy and controlling as a defense mechanism. Men too, I'm not being a misogynist. What that means for YOU is: it's possible that she's waiting for a more forceful man to come along and treat her like she wants to be treated. It's possible (don't go taking this as gospel) that she acts the way she does because she's hardened herself against opening up and feeling vulnerable. If you can find a man that's strong enough in personality as well as physical strength, she may let her guard down for him. This will allow her to explore all her repressed sexual urges and really "go wild." I think this sort of situation is what leads to the stories you hear about how a woman is a good faithful wife until the day she meets the new guy at work, new neighbor, cop, shopkeeper, etc. She may need a man to open the part of her that she's always fantasized about letting loose.
That being said, she may just be a tight ass and never get to that place. But if she's ever had a "wild side" or she had an overly strict father, if she's ever had a serious relationship with someone very religious, or she went to a very competitive school or work environment, she may have repressed the part of her that would relish being gang-fucked in a bar.
I know which part YOU want, the trick is finding out which outcome is the most likely.