If you have any influence on her grade, then I wouldn't go down this road at all. If you lead a discussion group that she is in, then I wouldn't go down this road at all. If you are not her teacher, grader, or discussion group leader, there's nothing wrong with a cup of coffee. If you get the perception that it's going to move to touching her boobies, then you need to check and make sure that it's copacetic with your responsibilities as a TA before she lets you fondle said boobies.
And I'm not being crass to be crass, I'm being crass to shock a point at you.