I’m not going to ask why your niece is living with you. The reasons for your sister-in-law not raising her own kids are none of my business. I do think it is important though that you are questioning the control your mother-in-law has over your husband and his family. I assume you went into your marriage knowing what the dynamic would be but maybe reality is dawning. Because of my up bringing I cannot appreciate or understand a life dictated by my husbands family but I can empathise with your deep rooted maternal need to have only your husband, new baby and you in your home. In my marriage I am my husbands equal in all things and I have drawn lines of no-crossing for both our families when in comes to our home, children and family life.
I don’t have children, but I used to babysit my cousins. I would let them watch tv sometimes, but if there was something on tv that I didnt think they should watch, I would change the channel, or turn the tv off. A Delta plane dumped jet fuel over an elementary schoolcausing minor injuries to children and adults on Tuesday. Planes dump fuel when they end up making a shorter flight than expected and the plane is too heavy for a safe landing. It wasn’t illegal.
I feel for your niece, she is not with her mother for whatever reason. Obviously you are providing her with a stable home. It must be a difficult time for her too. Maybe she feels that when the baby arrives you will not love or want her anymore. You could tell your husband that you want her to go and stay with another family member for the first few months after the baby arrives and that would be really understandable but she is at a vulnerable age and rejection could be very damaging for her.