Not sure how old mum is?
My experience of caring for my elderlies, they stop eating proper food when poorly/under the weather / depressed, and they never get back into the habit
She is grieving
But I would still get her checked over , it is a huge loss in a. short time , esp if she is just sitting there
Im going through the "got to get something healthy into Mum" stage now myself. Slowly her appetite has decreased, dry mouth, medications, food doesn't taste good to her. But the sweet tooth has increased
A salad now for her is just tomato and beetroot ( sweet ) , veg is just a toddlers size, a spoon of peas, a spoon of carrot etc. Any meat has to be very lean and a very small amount . Basically I put a toddlers size meal out for her, if I gave her an adult size one - she wouldn't eat a thing
Food also has to be softer
So I turn a blind eye to the sweet stuff, the biscuits and chocolates and I always keep tins of rice pudding and custard in the house jic she cant face a meal but every day I cook a meal for her - she will take a sandwich and yoghurt for lunch, porridge for breakfast - and just hope for the best
She gets lots of fluids, juice, tea, milk, squash