How do I balance my daughter and 1 on the way??

So to start off I have a 4 yr old from my previous relationship well now I have 1 on the way with my current GF. The relationship I have with my daughter is amazing! Me and the mother still get along no crazy break up and I get my daughter every weekend! My current gf fell in love with me and my daughter! My daughter loves her so much also! She we told her about the baby she was extremely excited!!!! Of course she wanted a baby sister but a baby brother will do! Win win right ?? Well idk lately my daughter has been getting not really jealous but she gets sad when me and my current gf are too close now or something and of course I chose to tell my daughter everything will be fine! As for my gf she's starting to get mad or hurt I guess because she feels my daughter can and will control me and her thing is that when the baby is here things will change! There will be 2 of them now but she says she can't get mad because she will look like the bad person! So idk.... how do I balance out my daughter my gf and our baby boy who will be coming in 2 months? Is it me? Or my gf overreacting? Idk any kind of advice would be great!