Is an outgoing girl romantically shy, or am I just imagining signs?

This got a bit longer than I had planned - sorry.

A bit of background -

The girl in question is somebody that I've casually known (friend of friend, etc) for about a year. We haven't had all that much one-on-one interaction in that time, though occasionally we've both gone to play various sports. (We both live on a college campus, so this isn't a big deal sort of thing.)

She has a very tomboy-esque exterior personality; she plays sports, jokes around with the guys, and all that. I say she is outgoing because she has an aura of being relaxed in casual conversation and jokingly flirts with people.

At the same time, she has a feminine side that it almost seems as if she is trying to hide underneath the tomboy thing. This is where I'm getting the shy vibes from - occasionally it will slip out from underneath the usual bantering personality she has on.

In class, I usually am sitting down before she comes in and she almost always sits next to or near me. Casual conversation will often be struck up before class begins, though nothing serious enough to be a signal in itself. During class, though, I'll catch her surreptitiously glancing at me repeatedly. She'll glance quickly with the corner of her eye, half adjust her hair while turning her head slightly to use her peripheral vision, or just appear to be looking at something else in my direction. If I notice and meet her gaze in time, she quickly looks away.

We both are on the same intramural sports team, and I've noticed a few things with that. Usually the team takes a few cars to get over to the field, so we are a bit squished room-wise. When we are sitting next to each other, I get the slight impression that she is pushing against me beyond just trying to stay within her space in the car. Also, she'll look sort of diagonally past my face with the side of her face at angle to mine, kind of glancing a bit.

I'm a pretty quiet person, so we haven't talked all that much. A lot of the interaction is her half-teasing me; you know, not an obviously flirting sort of conversation, but ironic comments.

The only other really relevant thing is some of her little facebook status messages - one of them was pretty obscure and when commented asking what it meant, she said that she was tired of being around couples and having nobody.

I get the impression that if she were interested in somebody, she wouldn't be nearly so blunt as she is when she's being casually friendly around friends. Instead, she'd be showing her feminine side and expecting the guy to make a move.

Now that I've just about used up the character limit dumping all the observations I've had, my questions:

Do you think she's interested? Why?

Do you have any suggestions on how to find out? (Please note: saying "ask her" is not an answer; I mean something more subtle that doesn't broadcast what I'm wondering. For instance, a sign that I'm missing, or a roundabout way of asking. I'm not out to destroy a friendship over my overanalyzing this.)
Is an outgoing girl romantically shy, or am I just imagining signs?
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