A.D.
Wow, I would be taken aback by that conversation too! Sam's Mom was out of line to make those assumptions. It would have startled me too, and in the moment, I would be a little hesitant for the right words. But now that you have some time to digest what was said, I would pull her aside the next time you see her at preschool and say, "Oh, say Jane, I was caught off guard when you asked me about DD's birthday party. I need to let you know that she is not having a preschool class party. She's only inviting one friend from preschool, X, and one friend outside of preschool, and the rest are family. No personal slight meant to Sam, I didn't want you to misunderstand."