Lots of sexual tension with a girl that has a boyfriend...

So I've known this girl for about 8 month and although there had already been a few hot situations before that, it's mostly since about 2 month that she has a started to be really flirty and touchy with me...

We're in the same class, we're both 17, the problem is she has a boyfriend and I don't know what to think of her and what she thinks of me...

There is lot of touching between us, if we're sitting next to each other our legs will often end up touching/rubbing (not lightly, and it's often her that 'initiates' it by 'involuntarily' touching me while picking up something etc, it then continues...). If we're near enough she'll sometimes also rest her shoulder on mine, she also often puts her hand on my thigh when sitting close.

She will sometimes link arms with me which will result in me pulling her closer and our bodies touching while walking.

If she (for some reason) touches my arm she will often hold it longer than needed with a lingering touch and she will sometimes hit me playfully...

There is also a lot of verbal (sexual) flirting between us and she recently told me that her boyfriend was jealous about her talking to me (although I doubt he knows everything...)

So what should I think of this girl and what could she think of me? This situation is extremely frustrating to me as there is a sh*tload of sexual tension between us and there's no way to release it right now...
Lots of sexual tension with a girl that has a boyfriend...
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