meh, you don't need a 'boyfriend destroyer.'
As far as I am concerned, unless the relationship is super strong and long-term, the fact that someone is 'dating' someone in college does not really mean shit. Honestly, you should NEVER assume that a girl having a boyfriend is a deal-breaker. Always assume it is on until she tells you explicitly that it isn't. Her saying "I have a boyfriend doesn't count," this can be interpreted many ways. Go 'till she says "no" (then back up and go again

).
Ignore the fact that she isn't single. If she brings it up dismiss it immediately and change the subject. Girls in general are always looking for the bigger, better deal; especially college girls who are super fickle. It sounds like she wants you, don't let a little bump like her having a boyfriend stop you from giving her what she wants.