Please Help Or Read more? ! ? Its About My 3 year old daughter?! At my wits end?

Im 39 weeks 3 days gone. The doctor said that i would most probably have to be induced if it does not come on time. I am having a girl again. My 3 year old is called Hannah. The problem I have see, is that she gets jealous of the baby on the way and even told her dad (my ex) that 'mummy doesn't want the babe'.This is 100% untrue. Me and my Fiancee love her and show her all the attention. She has got a big bedroom, she can come and get us whenever she wants, she goes out playing in our garden with my Fiancees little boy(4) and they play lovely. She doesn't share a room and we live in a big house. When my fiancees little boy has friends over, she has our next door neighbors girl over. She gets so much love its unreal. And now, she threatens to hit mummy's tummy, and lies all the time. When she doesn't get her own way, she will pee on the floor or over herself. 2 days ago, we had a family day to the park, which is about 2 hours away. On the was back, she spotted a burger king. We had already had dinner, which she had refused to eat and only ate dessert. We were tired and drove past. Then she starts wailing. Then about 5 minutes after the wailing, she pees all over the car and even a bit on her step-brother? What Can I Do?