@Background Pony #F55B
I say pokemon with telekinetic ability, that can speak human language or can sign that they want to do some private battling. This would also depends on he taste of the trainer for example with Valerie it would be fairy type and Sylveon for obvious reasons. With Olivia it would be Lycanroc.
@Dirty Bit
They aren’t that memorable in X/Y nor Sun/Moon to be honest (and you fighter her friend more than her in all versions of S/M/US/UM which doesn’t help).