Asking Eric: My ex let his brand-new girlfriend babysit our son. Am I wrong to be mad?

A mother is seeking advice from R. Eric Thomas after her ex-partner allowed his new girlfriend to babysit their 10-year-old son overnight. The mother expresses significant concern and anger because she has never met or spoken with the woman and knows nothing about her background. She disagrees with the decision made by her ex and his partner without her consent, questioning the safety of entrusting their child to a stranger during a sudden schedule change.