Ouch.
No, you shouldn't have. Probably nothing you can do by way of direct amends--at least until/unless you know what happened as a result. For all you know, her sponsor said nothing to her--the sponsor might have taken it with a grain of salt and decided unless she came and fessed up, to leave it alone.
In this instance, maybe you can make an amends indirectly by deliberately doing something kind and helpful for someone you don't particularly like. Going out of your way to extend a hand or lend an ear to someone who annoys you or has harmed you in some way. Just a thought. Might be a good exercise.
You could, however, apologize to the sponsor when you see her.