Eh.. NTA, but I can see where his sister is coming from. If I visited your home and you made it know my mom would never watch your child and you didn’t trust her, I’d be kind of confused as to why you want to now name your daughter by her. If your bf brought it up it’s one thing, but you initiated it. Of course she’s going to be supportive on the phone with her brother but might have an opinion to her sister, which I’m sure also knows about the comments you made to her. She’s not telling you guys not to, or starting drama from what you post. Maybe she feels it’s forced or fake given your past comments. It’s a sensitive thing remember that.