My Tenager is jealous of my new to come

Plz help me what shall I do ? I have 3 kids already one is 11 who is behaving very bad since she knew I’m pregnant with baby no 4 and 5 my younger is 6 and my oldest gave pain to her, I found out it’s cuz of jealousy. And now I’m pregnant with with baby no 4 and 5 and she don’t want them even to come to this world. She gives hard time to my youngest since recently :( what can I do plz help!