Is It Worth the Argument?

Question...In a co parenting relationship at what point should you question how much time the other parent is spending with the child? Allow me to explain this a bit further. Let’s say you are in a friendly co parenting relationship. Parent A is the primary caretaker of the child and parent B gets the child on weekends. However, parent B has a part time job and other obligations on the weekends that keep them from being home with the child. So when the child goes with parent B on their weekend the child is being watched by parent B’s significant other probably 65% to 75% of the time. Should parent A have a problem with this? Is it parent A’s place to bring it up? What could be a possible resolution to this problem? Is it more of a problem that parent B’s SO is watching the child? What do you think?