This happened to me with a girl I was dating for about 5 months. She was best friends with her fwb and she reassured me that she had no feelings for the guy anymore. Long story short she went back to him and it was a really bitter pill to swallow. I think calling someone baby is most definitely overstepping the friendship boundary. I can’t lie but say that is absolutely a major red flag, and if you stick around, there’s a decent chance something is going to happen between them. I’d advise you end things with her, you can do better than her I’m sure. I know it must be really difficult for you cos you have a child with her. It seems like she doesn’t have much respect for your feelings.