My opinion in Girl's-World is violence is never a solution and only appropriate if she felt physically threatened...... did she?
Although your chivalry is honorable, she may be a little put off by your inability to see that she's capable of handling groping, loser on her own.
It would be completely different if she had asked you to help her with the situation, which I'm assuming she didn't?? It seems (to me) the way you described things, your reaction has more to do with defending your manhood than anything pertaining to her or her situation.
-------------------- life may not be the party we hoped for, but while we're here we should dance..