The office theft?

I need advice. I've hit it off really well with a cute girl from the office. She is a few years younger and we've been spending a lot of time together, but mostly at work type functions. She gives lots of IOI's and responds well to flirting, email / texting, etc...
BUT, I'm told (recently) she has a boyfriend.
I've never asked because I don't want to create a frame where:A. I know, B. I care-she is chasing me right?
She's never mentioned it, and had plenty of chances.

So here is my problem.
I don't want to be a slimeball, but she is right out of college, and this rumored bf might or might not still be in school. I feel like that is a time when a lot of people breakup anyway, so I think at a min, she is thinking about breaking things off with him.
Regardless, I want to ask her out, but ever since I heard about this bf, my head is messed up. She is acting the same, but I'm creating drama in my head.
I also don't want to make things weird. She is in a different division, so there are no ethical issues, but I don't need a cute little reminder of my failure running around my office all day if I happen to push too hard and creep her out.

Am I just barking up the wrong tree?

Ok, first, SHE hasn't told you she has a b/f, it's a rumor you say. Therefore it's not valid until she tells you.

Second, she's showing interest, so escalate. You apparently already talk to her privately through text and email. So, invite her to meet you and hang out somewhere. If you haven't yet hung out with her outside of work, but you two get along well together, invite her to join you to something outside of work. If you have already, even once, done that, the comfort/trust is already there, so simply invite her again to do something. After a couple of times of this you could escalate back to your or her place.