Is this enough in your view ?

Please stick to your boundaries and remember age is still just a number. She is plainly lonely but wanting to have things her way ( naturally) you must stay firm or more resentfulness will occur. It might even be kinder to be straight with her. There is nothing like honesty.
Maybe you could work together to ensure she has at least a day a week from one of you to look forward to for something to even if it’s not as much as a whole Sunday lunch.

Thank you all for your helpful messages. I think I know the answer really - I suppose it feels sad to see someone lonely but know you can’t completely fix it. Part of us probably subconsciously knows its how it might also be for us and it’s a scary thought. I am very grateful for your messages. Have a lovely day !

You all sound lovely. I don’t think your mum realises how Lucky she is, I would stick to your boundaries, they’ll come in useful when she’s 90 like my mum, and has outlived all her friends and relies on me, an only one and two grandsons for company. The guilt is terrible, and I honestly don’t know how to deal with that either.
I agree it’s very waring. I visit mum twice a week, because she is so miserable when I visit, it takes me a day to calm back down again.

You sound like a lovely,caring family and your Mum sounds alright,too. She is missing her husband still ,that constant company that you get used to and that is probably why she wants to be with you so much. Just natural really but I am sure she will know deep down that your own immediate family comes first. Having lost another friend last week myself to an unexpected heart attack ,it does shake you up and make you feel a bit isolated knowing they are no longer there to chat with.

Don't allow her to guilt trip you. As 'Dad passed away a while ago' I expect that she's still adjusting to living alone. Perhaps she'd enjoy a regular Zoom meeting with the family? We do this weekly, although there's no obligation to always check in.

I do hope my children aren't doing 'duty visits'. Sometimes I feel that they visit too often (and stay too long) as I get tired.

It is sadly a common issue in this board

You have to decide how much you can do and set boundaries

@GrannySomerset - I don’t mind some woes, that’s life but all the time can get a bit much. I simply ‘mmm hmm’ at them !

Outliving friends must be miserable. I can’t imagine how that must be….

I’ve suggested U3A - she plays scrabble/ other games on her ipad … she uses email and also still drives. I’ve suggested some volunteering maybe reading at a school (she could sit down and small chunks of time). All met with a ‘oh that’s not for me’ response !
Thank you for responses so far !

Mum has friends, although some have died - she plays cards, visits gardens, has lunches. All of this and still it’s not quite enough

One problem of age - outliving your friends and perhaps siblings.
Some people are quite content with spending time alone at home although they also enjoy outings with friends. Others can't bear to be home alone.

Does she have an iPad or tablet? What about suggesting she joins Gransnet? Wordle? Solitaire?
wordfinder.yourdictionary.com/blog/best-free-online-word-games-for-seniors/

No helpful advice but your post is an Awful Warning to those of us living alone. As a friend of my dear MiL said to me, “Nobody wants to visit a miserable old woman so I keep my woes to myself”. Excellent advice which I try to follow! I