Cshapiro- I thought about this again and decided that the best way is definitely to talk to your Chosson. Your friend will probably not understand why you are so horrified.
You might as well stay good friends with her, and at the same time prevent something like this from happening again.
I just hope your Chosson didn’t think the you sent your friend to get some $$ out of him! Boy, I’m making matters worse, am I not? 😉