I would have smashed the brakes on as well. I am certain other parents have no clue about all the arrangments..she can't be the only one with a sensible parent. Good grief! What are the 'hosting' parents even thinking. You say you don't know them..however they can't possibly be 'parents' to their daughter if they are promoting this..sounds to me like they just want to be buddies and good friends to their child.
You have NOT over reacted. Let her get mad. She will thank you later ..believe me. Hang in there