Husband's Child Support

CeeTee • Mom. Wife. 25. 🐞Harper 4•25•17🐞 🐝Ava-Cate 9•24•19🐝
Hi everyone! I need some help. My husband has a six year old son from a previous marriage. 
Here's a little background: they were only married 6 months. Three months after my stepson was born she got pregnant, by another man! Needless to say they got divorced. She use to live in a different state than so my stepson went to school in that state. He currently lives with my husband's mom in that state to finish the school year, as his mom moved to the same state as us with her other children to live with a new boyfriend. I know confusing right. 
My husband and I have been married for three years and we are currently expecting a little girl in May. Once his ex wife found out I was pregnant she tried to file for child support. I have nothing against my husband paying child support. But my stepson does not live with her. He lives with my husband's mom. We get my stepson every weekend because of school.   
This whole situation really annoys me. I try to talk to my husband about it and he's so relaxed about it. Ik it's my hormones partly but this lady gets under my skin. She's always been so rude to me for no reason. And I will not allow my husband to pay her money each month when my stepson doesn't live with her. Any advice?