Grandmother admits depression due to loneliness, but doesn’t want to move nearer to us. Suggestions?

My nan is clearly very lonely, she lives alone (my granddad died over 25 years ago) in a bungalow in south London that they shared for many happy years. My mum and her husband moved to Suffolk roughly 10 years ago and I followed suit a few years later. The only immediate family member left in London is my sister and she has decided to move up here as well. Nan has lots of family members in London that help her out and spend time with her on a day to day basis (she is one of 10 children) so she has a huge network of neices, nephews, cousins etc. who not just want to help out but enjoy helping her because she’s a really fun woman to be around. Nan has always been slightly annoyed that mum moved away and doesn’t particularly get along with the idea of my step father because of this. In recent years she has had a decline in her eyesight, she has to have an eye injection once every few months and it’s incredibly stressful as you could imagine. The fact that my mum isn’t there to help her or drive her and it falls on other family members has become a real source of tension. So for a few years now we’ve been suggesting that she considers moving up to Suffolk, with a view to her living close to us in a retirement home. We all want this to happen but she clearly doesn’t want to. She says to us every day how lonely she is but the second we suggest it, she tells us how much she’d miss everyone who comes over on a daily basis. I don’t think it would be wise to talk her into such a huge decision because my mum and step dad need their space and I worry that if we talk her into it and she doesn’t get to come for dinner every single night then it will make matters worse? Equally it’s become a huge source of tension between my mum and my nan with them having regular arguments over the phone. It upsets and affects my mum as well and makes it really difficult for me and my sister to call her daily because we become stuck in the middle of an impossible situation. Please help.