If your child is named Emerson, and wants to go by that name, but his stepmom insists on calling him Emmy (and he's said to stop), WWBTAs if we started calling her by a nickname she doesn't like?

My son is 9 and is called Emerson. Not Emmy, not Em, Sonny, or anything. It's Emerson. His stepmom has been in his life now for almost two years (dad got married fast) and has insisted on calling him Emmy starting about 6 months ago. He asked her to stop several times. Dad doesn't see a problem with it and is like "It's indeering". I said it's a problem because our son doesn't like it.

Stepmom's name is something that can be shortened one of two ways, and she doesn't like the other way. Think like Katherine but she goes by Kate. Would my son and I be a-holes if we started exclusively calling her Kathy, which she hates?

Just trying to figure out how to get the point across. It's just disrespectful at this point and I never realized how much it bothered my son until recently. Now I tell her all the time his name is Emerson and to stop calling him Emmy.