WIBTA if I continue calling my MIL after my SIL asked me to call her Mrs. [last name] 3 years into my marriage

My SIL and I/my husband had a disagreement/misunderstanding about something unrelated, and in repairing that, we each asked each other what we could do better. I was expecting the response to be related to the disagreement we had, but instead she told me I should call my MIL (her mother) by Mrs. [last name]. This is after three years of marriage and calling her by her first name.

My MIL and husband never told me what to call her or corrected me at any point since before I’ve known her to this day. Confused why my SIL thinks it’s appropriate to request this. It feels like a power play on her part, and I don’t want to change how I refer to my MIL when she didn’t ask me to. I know I could bring this up with my MIL, but I would prefer to avoid doing so as it’s been three years. Furthermore, my MIL and I have been through a lot together, and I frankly don’t want to refer to her as Mrs. [last name].

My husband and I lived with her for a year during major medical issues on both sides, both her’s and mine, and we mutually took care of each other. This just feels like a slap in the face from my SIL. WIBTA if I keep calling her by her first name and pretend my SIL never brought this up? TIA

OP has offered the following explanation for why they think they might be the asshole:

It might make me the asshole because it might not be that big a deal and maybe I should just do what my SIL wants.

TOP COMMENT

This is the right move. You find out for sure if your MIL is comfortable being called by her first name, and if it’s a power move by your SIL, you’re shutting that shit down right away. NTA.

Edit: Fun story, I never knew what to call my MIL and was too uncomfortable to ask so… I never called her anything! I was always saying hey or something to get her attention.

REPLY

Haha! I try to do the same thing too with my MIL. We’re okayish with each other. But Mom feels too personal and (first name) sounds to formal.

RESPONCE

I call my MIL by her first name but I only need to do so about every 5 years, I usually just work round it by getting her attention another way. It feels awkward and I don’t really know why. We get on ok, but we’re not close. It’d be a cold day in hell before I ever called her Mum!!