How to deal with MIL

I just got married this past august this is supposed to be the happiest time of my life we are expecting our second child together a little girl we have a 3 year old boy already. Instead of being happy with my new husband and pregnancy my mother in law has made my life and relationship a living hell. I am considering divorce we argue constantly because of her. She is always trying to dictate our relationship making everything about her and my husband sides with her because she cries and put on a show as if shes so hurt. I have my son fully potty trained she wants to put a diaper on him bcuz she doesnt want to bring him to bathroom at church. I say no. She complains well he needs a diaper when he gets in the car no he doesnt i toliet him before we leave the house. She dictates everything we do and how we do it i feel i never have a say. I let her take control of my so. Babyshower and my son birthday party with this little girl i am enjoying shopping for her doing the things i couldnt do for my son. I pretty much have everything for my son. Shes insisting on a shower. Right now my husband isnt on the best terms with my family and although i respect him and his family and he doesnt respect mine i dont want the shower being akward so i said ill pass on a shower i have everything for her already anyways. But shes pressuring me and saying i have to how can i have a shower for my son but not for my daughter how would my daughter feel? I said she will feel fine because i dont have to have a shower to show her love. The whole situation is making me uncomfortable and its like everything has to be her way or she throws an fit and cry to my husband. And i cant talk to my husband because everytime i try its thats my mother dont talk about my mom. Its becoming to much and idk what to do. Rhe constant arguing is starting to affect my son and its not like we are arguing about anything other than his mother trying to interfer or dictate our lives.