Well I think it's her drink. She later grabs the bottle from among her stuff on the table, where it would be placed had she poured the glass with her likely dominant right hand. Conjecture obviously, but her grabbing the bottle later also kind of shows she thinks of it as hers. And why else would she grab at the glass?

Also as you can see in the screenshot in the post body this is her rejecting him after their second date, so that is another indicator for a retaliatory motive on his part. Which would also explain the absolutely reckless level of violence he employs, literally kicking her when down and slamming her head into that bench at the end.