...on your LO, what would you do?

We have been struggling with what to do about this for about a good month now. Unfortunately the kid I am referring to is LO's cousin. It started off as her excluding/ignoring LO at times, now it's that and other behaviors we aren't ok with. Using teasing words, being one of them. I know the kids are only 4 but LO is glued to her cousin, won't branch out to other kids, and soaks in all of her behaviors. So far we have just casually talked to LO about asking new friends to play but would love to try something else...

Her cousin was over to play the other day and she shows some of the behaviors here too, so I know it's facts not just what LO tells me.

Any advice?