Just a few suggestions regarding meals - please feel free to disregard if they don't suit you, your Mum or your situation. Often what works well for one family won't work for another. Years ago I discovered that Dad was living on McDonald's for the time Mum was in hospital because he "didn't like pasta" (I'd made a few pasta meals to help out) and "Wouldn't eat that rubbish!" (I'd put in a stock of instant meals for him to just heat and eat). I might add I had asked first what he would like and he'd said "Oh, I'll eat anything!". He didn't have dementia - just old and set in his ways!
MEALS:
Anything you can find in your Mum's cookbooks that you remember her cooking - her age group usually had a selection of meals (either cut out of magazines or in an exercise book). She may not have used these recipes for years (because she knew them off by heart) but you might find them if you look.
Simple "nursery" food - stewed fruit (tinned) and custard (bought); porridge; jelly; soup (tinned); mashed potato; grilled chop or sausage (if she can still chew well); steamed vegetables; simple salads (tomato, lettuce, cheese, etc).
Anything made with mince! You can chop up heaps of vegies very small and add them to mince for a healthy and tasty meal. Buy first quality mince if you can afford it (fat levels are lower). Add chopped vegetables - onion or shallots, tomato, celery, zucchini, carrot (grated is best), egg plant, capsicum, finely cut cabbage, cauliflower or broccoli, mushrooms, etc. etc. etc! You can also add tinned food (tomatoes, mushrooms, etc.) or frozen (eg. peas, beans). I usually add a generous helping of pasta sauce (bottled) to give extra flavour, but this depends on taste.
You can serve the mince alone, on toast, with pasta, rice, mashed potato -etc!
If your Mum needs calories, try milk drinks (Milo, Ovaltine, etc.) and / or "smoothies". I put a banana, a spoon full of yoghurt and a cup of milk into the blender and make up a thick and delicious drink that way. You can vary the fruit and add honey if extra sweetness required.
Tinned fruit (preferably canned in its own juice rather than in syrup) with icecream, if she can manage the cold of ice cream.
Try baking in the Weight Watchers way: a chicken is a good start - place the (defrosted) chicken on a small wire cooling tray in a baking dish. Add water to just below the chicken. Cook in a moderate oven (180 degrees C ) for about 1 and 1/2 hours (or more, depending on size of chook!). On a separate shelf in the oven you can bake some potatoes, carrots, sweet potato and pumpkin - just prepare and wrap in foil. This is a "low fat" way of cooking bt easy and healthy and tasty. I don't peel the carrots or potatoes - just give a good scrub. Pumpkin and sweet potato need peeling though!!
You can bake all sorts of meat in the above way. Also don't overlook grilling, or "dry" frying using a non-stick pan and perhaps a little cooking spray.
I realise you may well be doing many of the above (if not all)!! (I apologise if I've been preaching to the converted!!)
My main advice is to find a few things that are successful for your Mum and repeat them often! Don't feel you need to be a "gourmet cook". Even if your Mum won't eat pre-prepared food, she might like packaged desserts (yoghurts, sweet creamy puddings, etc.) and don't forget the cake shop!! The occasional meat pie or apple pie are cheap and make life easier when you are rushed!
Good Luck!! Nell