Mother-in-law wants to be known as ‘Nana’ and I don’t want her to be

Utterly ridiculous statement. “Nanas” don’t get a say in anything. It’s their grandchild - not their child. The sheer entitlement of some grandparents is breathtaking.

I don't think you're being unreasonable at all and I bet most of the people here saying you are have no idea what it's like to become a mum while you're grieving for your own. My mum died a long time ago but when I talk about her to my DC I refer to her as their Nana, because that's what she would have been called. Even if your mum's no longer around, she has a place in your family and you can only keep her memory alive by talking about her and giving her a place in your children's imagination. I bet if you talk to your MIL about this she will completely understand, especially if she's lost her own mum

This nails it for me. I can’t imagine anyone with your best interests at heart not seeing where you are coming from.

sorry OP, I fully understand why you are finding that difficult. Being a new mum when yours in no longer here is heartbreaking.

What an incredibly unkind thing to say and utterly lacking in empathy.

You can have the best laid plans and they may go awry. Children make up names, have things that remind them of that person, have a speech issue that changes a name.

Could she not be a nana (mother in law’s name)? That’s what I am (there are lots of us)

Yes I'm sure her Mother in law would be understanding, because she seems to get on immensely well with her 💚

This.

If you talk to her surely she'll understand - she doesn't know that it was what your mum was called by her other grandchild.

It's quite odd that she wants one grandchild to call her Nanna and the other Nanny - when they talk to each other about her won't they correct each other or assume they're talking about different people if they're both quite young? Although even more likely ypur child will copy their older cousin - surely she wouldn't correct one cousin and say "I'm Nanny to Freddie but Nanna to Oli" the way you might tell Freddie that you're Mummy to Oli but Auntie Lisa to Freddie...

I'm surprised at the "Nanna women are Nanna! No debate!" answers. In reality humans rarely name themselves, and the titles small children use tend to evolve from the children themselves and what they hear others calling the person (here the other grandchild is the obvious peer to learn from) so your MIL would be asking you, your DH, and other relatives (parents of the other grandchild? Other grandchild?) to call her Nanna when talking about her to your child for it to "take".

I would imagine that your MIL will be completely understanding if you talk to her and explain though - I certainly would be if my children's partners were in your position.

Not unreasonable. Be honest with her, tell her you don’t want to come across controlling or being awkward but its hard for you to hear. In my DIL said that to me I wouldn’t be offended at all. In fact, I think i’d check with them before announcing if i’ll be nanny / nana etc

Probably because she will never hear her own mum referred to as Nanna by her child? It isn't like hearing the name in passing is it? If you were comparing it to the word mum it would be more like how you would feel if you had to start referring to someone else as your mum after losing your actual mum.
I've not lost a parent but I can still manage to have empathy and understanding.

My two Nan’s were both nan, but we differentiated by calling them by nan ‘their surname’ so for example my mums maiden name was corn and my dads surname was flake, they were ‘Nan-corn’ and ‘Nan-flake’. It was the other way round from your situation, I was the 14th grandchild on my dads side & the first on my mums side but all the grandmothers on both sides had been known as ‘nan’ and neither were willing to budge. HOWEVER me and my sister both did start calling nan-flake ‘nanny flake’ instead because we heard one of our younger cousins calling her nanny after nanny McPhee & that new name stuck for ever, so your baby might mimic her cousin & not call her nana anyway.

I hope you can find something that works for you. Could your mum be Nana Angel or another special name that sets her apart? I am so so sorry for your loss, it’s especially poignant at this time of year & I really feel or you navigating this.

can you tell your MIL how you feel?

Well both grandmothers can have the same name. Mine were both gran and my husband’s were the same. It is up to her what she wants to be called but if she’s lovely and already gets called Nanny just say what you’ve put here and she’ll probably change. I can’t imagine she’d be that bothered

I liked Grandma but my DiL’s mother is known as Grandma… to previous Grandchildren, so I was asked to pick something else…. Which I did… no problem, no confusion of who’s who in our family there is only one Nanna and that’s me. Only one Grandma DiLs mother and ex’s wife Nanny… makes it easier no confusion…. Maybe you suggest if she keeps the same name as she is known to the other Grandchildren, they as in the GC don’t get confused. Good luck x

Yes completely concur with you
I was just thinking the very same thing, she worded it so beautifully brilliant here - She just needs to reiterate to her husband & let him, I believe, be the messenger 💚

You are being very unreasonable. My mother is dead too but I’d never behave like you.

Your mum was unique and precious and it's deeply sad that she was in the life of your niece but not of your own child.
But... 'Nana' is a common term of address for a grandmother. It might feel painful to hear your mum's first name applied to somebody else, but it will happen all the time because names are shared around. Maybe you could think of 'Nana' like that.

I too think you should tell her how you feel. I’m sure if she’s a nice woman who loves you and is already called Nanny by other family she’d understand. At the moment she doesn’t know how you feel,

Just explain to her how you feel. If she's as nice as you say, she will most probably understand. How about suggesting another name, like Gran or Granny? If she's desperate to be Nana, make sure you refer to her as Nana Joan/Susan/whatever to distinguish from your mum, Nana Mary/name.
I called both my grandads grandad and their name and it wasn't confusing.
I hope you're OK, it must be a very emotionally draining time for you having a new baby and losing your mum relatively recently.

YANBU

Honestly I'd just explain it as you have here. Tell her you'd really appreciate her remains Nanny.

im sorry about your Mum xx

Talk to her, explain it the way you have here. If she is a decent person (unlike some PPs) she will understand and just go with Nanny.
You have good personal reasons for not wanting her to be Nanna, as MIL is Nanny to someone else, it sounds like it's just a preference.

Who chose the name Nanny?

Did MIL want to be Nana but the other grandma was using it?

I wouldn’t say anything directly but would maybe ask why she wants a different name. YANBU to feel the way you do.

Could she be Nana with her name: Nana Joan or Nana Patricia?
My gd has two Nanas but we both have our first name included. Might help not to associate with your dear Mom. Also when you talk to your baby as they grow and show her pictures she could use your Mom's name too.

Just always refer to her as nanny… problem solved