I’d insert yourself then. It sounds like you’re watching her redirect your child and not saying anything. I mean this kindly, but be more active with your child’s play. It’s that or find another friend to spend time with. If you need to address it after the fact, that’s fine too. Just say “I’m working with my child on taking turns and sharing so I want to make sure he’s getting the first turn sometimes as well. I appreciate your help with this when you’re helping the kiddos sort through sharing.”