When/how should I re-establish contact with her?

Last summer I hit it off with this girl, but then college started again and we didn't hang out anymore.

In the meantime she's started dating another guy. :( And I really don't like him, he's immature and rude and super clingy...

She seemed to hide him from me for a while until I figured it out and asked her about it. We talked, and I confessed that I'd liked her since summer, and her response was "you never said anything". Just when it seemed she was going to confess she'd liked me too, she suddenly snapped and got really angry with me, saying we were never friends and that she didn't think friendship was in our future.

And she cut me out of her life.

She's studying abroad in China over the summer. I ran into her right before she left, it was much more positive, but very awkward.

How long do I wait before I try to regain contact, and how should I do so? Should I contact her while she's traveling and far away from the other guy? Or should I give it more time and wait till she gets back? And how do you regain contact with someone who tried to cut you out of her life, what do I say?
When/how should I re-establish contact with her?
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