Telling your child about new baby❤️

So I finally told my4 year old daughter she's gonna be a big sister soon! & she was super excited at first but a day later she came home from her daddies we are separated and I'm with a new guy for 3+ years now and she keeps saying she doesn't want the new baby and she isn't sharing. But then she gets excited again? She named the baby and says it's a girl and she's gonna love her. Witch I'm super excited about but I'm super scared with her on the other hand saying mean hateful things about the baby! Is this normal? I'm so lost and don't no how to react besides say that isn't nice? Any advice ?