Am I wrong?

My baby shower is planned for June 6. We invited mostly family and a few friends. For some reason my father in law (who's not even going because its all women) decided to invite a woman I have never met. I threw a little fit but it was obviously too late to do anything about it. Then the lady asked if her daughter could come. We told her no children but now other people are asking if their children can come. We have been telling these people yes because we have known their children for 4-6 years. My niece, who is hosting the shower, is saying that its unfair and wrong that we said no to one person but yes to the others. Am I wrong here?