My babygirl is jealous?

I’m 18 weeks pregnant and my baby is 8 months nearly 9months. We found out our gender , next baby is a babyboy! But recently, i guess my firstborn notice? Or can sense that she won’t be the only baby in the family. She starts being so clingy and you know rough. Usually ppl say, it’s because you are having a baby boy that is why your firstborn is quite rough. Is it true? She is just rough but clingy cute i mean it’s cute but do you think she sense she is going to be a big sister and she is jealous? Any tips