My daughter has a friend "Sarah" at school that she is constantly comparing herself against and trying to "best" this friend.

"Sarah has a pretty dress, so I want a pretty dress"

"I told Sarah that my hair is longer than hers" (longer implies prettier in my daughter's head).

"Sarah told me my dress is not long." (Cue crying and asking for a longer dress).

How do I deal with this?!? I told her that it doesn't matter what anyone else thinks. Honestly it seems like Sarah is her frenemy and my daughter would be better off not talking to her!