My mother-in-law refuses to call my son by his name. Is it petty to stop showing up to her Sunday dinners?

My husband and I have been married for 4 years. My husband also has two kids from a previous relationship. His ex wife has always been close to my MIL. So close that my husband's ex still shows up to family dinners. I didn't use to mind because my husband and her have kids together and I thought that it was good for their kids to see their parents getting along.Anyway, my husband and I have a 5 month old baby together. My husband's family is Italian American and all of the grandchildren (my stepchildren, SIL's three kids, and BIL's two kids) all have Italian names. I am not Italian and my husband and I opted to not give our son and Italian name. We gave him a name that was important to us.Instead of calling him by his name she calls him by an Italian name. The name isn't even connected to my son's name. It's a name that she wanted to use but never got the chance to.I feel like this is the last straw. She has never liked me but now she is calling my son by a completely different name. I have talked to her about it and she says that we should have just given him an Italian name in the first place. My husband has talked to her and has gotten the same response. He's tried of it as well.Would it be petty to stop showing up to her dinners on Sundays? via /r/Parenting http://ift.tt/2lF8oFN