I'm going to tell a babysitter to do her job at a play center
Does the babysitter not do her job correctly?
She was neglecting the children and not listening to their needs.
You must have felt badly for the children in that situation. If you feel the need to talk to her about her workplace behavior, try to do it in a professional manner.
I may explain to her how immature she is so she never does that again.
Make sure it is just you two around when you reprimand her. You do not want her to be embarrassed around others and you want the advice to stick.