Does she though, Bluelady? Nowhere is that stated by the OP.
She mentions meals and lawn mowing but not whether the DM is able to cook or might like to cook, or needs support or hand holding.
Sometimes getting back to doing your own cooking, cleaning, shopping, and in general establishing your own routine can help you get back on your feet.
Additionally, it can be jarring to an older person to have a lot of continuous contact with preteens and teens too, especially if going through grief. The OP has not said much about what the DM might feel about four weeks of close contact with children at an age when they can be inconsiderate, stroppy, cheeky, eye-rolling and quite unpleasant company.
An aunt of mine lost her H two years ago (married in 1966). Her two children have helped her out quite a bit as she is living on a farm - this was their routine for many years anyway despite both having jobs, one involving travel, and one holding down a job while doing an engineering degree and having four children in about eight years. My aunt found she wanted her own space though, so after a month started to turn down invitations to dinner and outings and definitely shuddered at the idea of a holiday - she felt she would cramp the style of the children, ranging in age from preteen to baby, the DCs' cars would only fit their families - four children plus car seats in one and two in the other very compact car and my aunt is an amply endowed lady, so she would be left in a rented house all day by herself if they went on an outing and wouldn't even have the comfort of her own surroundings or the possibility of a friend dropping in for a cuppa. Not every child wants to go to a beach every day, and the weather isn't always beach worthy. Elderly people don't always feel up to sitting out all day in the sun on a beach either. Loos are few and far between, often in an atrocious state.
My aunt is 87 this year so 85 when she was widowed. Her idea of dressing for a day in the city with my mum is the kind of clothes people wore in the 60s if they were nicely turned out - smart and uncomfortable shoes, good looking mac or coat, fancy handbag, makeup, cloud of perfume, hair sprayed firmly into place. I very much doubt she has a stitch of clothing that she could wear to a beach.
I don't think either the friend or the OP have thought this through at all.
The friend sounds like someone doing some shit stirring in the emotional aftermath of bereavement. This is how some people cope with the emotions associated with losing a loved one.
It's understandable to have irrational thoughts and to have unreasonable, strong emotions after a death - I think the OP should see the feelings/venting of her friend in that context, but should not give any of the complaints much weight.