Different names for grandparent-AIBU?

[JessieMcJessie]

My MIL is not from the U.K. When DD was born we asked her what she’d like to be known as. She said she’d like DD to call her by the word for Granny in her own language.

DH and his siblings were all raised in the UK, FIL is English and none of them speak MIL’s language.

DH’s sister has two kids who call MIL “Grandma”. MIL told us on the quiet that she now regrets not having asked to be called her own-language Grannie-equivalent name by them, but only came to realise that recently (they are 8 and 11).

DD is now a toddler and is saying the name really nicely now, but it turns out that SIL is actually really unhappy with the cousins using different names for the same person. She’s pissed off at her Mum, not us: I think that she feels it is some sort of favouritism thing.

AIBU to feel that SIL is over-thinking this? Is it not fairly common for different names to be used, for all sorts of reasons? My cousins called my Granny “Nana surname” and my brother and I called her “Granny first name”. I never gave it a second thought.

Thanks everyone. I am very fond of SIL and don’t like her to be upset but I am glad that most people don’t think it should be a problem. I think that possibly she has realised that MIL’s background is not something she has ever given much thought to, whereas her brother, my DH, has taken a bit more interest lately and MIL has responded very positively to that. It’s not a huge family rift or anything though, just a little niggle that she mentioned to her brother- it came up when she realised that when she was talking to our DD about MIL she’d have to use “our” name or DD would get confused, and she said it was too much hard work to have to remember the difference. We’ll explain to DD of course that people can have different names but she’s only just two so a little bit small to understand that yet.

My sister’s kids call my parents Granny and Grandpa Portsmouth (I’ve picked place name at random), and sister will call them that when talking to my kids. They understand who she’s talking about fine. Don’t worry about it too much :)