L.U.
Sounds like the little girl was driving her nuts! She is tattling and grabbing her arm, I certainly wouldn't make my kid play with her. I would probably just say to my kid, "Look Sarah, I know that this little girl is driving you batty. You certainly do not have to play with her. But you can not be rude."
I think it's silly that we tell our kids they "have" to play with everyone. Personally I see some kids that I am glad my children have chosen NOT to play with them. So, I have always told my children that they can say, "no thanks. I am playing with someone else"
I may get boo'd but, it works for us!
L.