Step Children, Help

My husband has kids from a previous marriage. they are wonderful, but I never noticed how spoiled the 4 year old was until I became pregnant. this is my first pregnancy, but his 4 year old is his baby. she gets whatever, whenever she wants. she STILL will break into our room at night and crawl into bed with us, I am REALLY concerned. Will she be jealous? Will she be coming in waking baby? I am just SO nervous about what will happen. I love this little girl, but I love my unborn baby too. any advice? I talk to my husband and he tells me this is just her age, once baby comes she will be done with it. i just don't want to be fighting off a then 5 year old to keep my baby safe/asleep.