Step daughter

Alyiah

So I have a 4 year old and my bf has a 7 year old. We are currently pregnant and are starting to have some problems. My step daughter was basically raised my her grandmother and father. Her bio mom was around for some time but eventually decided she didn’t want to be a mom anymore. My step daughter is very shy and stand offish towards me. I try to talk to her or get her to do things with me but she wants no parts. She also never wants to come over to my house because she wants to be with her grandmother. In the same breath she is saying she feels like she’s being left out and it will continue once the baby gets here. At this point I don’t know what to do.