pasta and tomato sauce - she can make a large batch of it and freeze/defrost as required.
Fry onions, red peppers, add tin of tomatoes, and a pinch of basil/oregano, simmer for 10-15 mins, serve with pasta of choice and a sprinkle of cheese. I lived on this as a student. And I would live on it now if DH would let me. If she is feeling fivolous, has guests, wants to spruce it up if feeling flush, she can add a splash of worcester sauce, splash of wine, courgettes, or spinach, stir in a spoonful of pesto sauce, that kind of thing.
Great eaten on its own, or with crusty bread/salad.
or
chickpea and potato curry - fry an onion, add peppers if desired, and diced potato, stir in couple of spoonfuls of pataks curry paste, add either coconut milk, or tin of tomatoes, or even cook with milk (i often do this to add creamy texture), cook for 10 mins, add chickpeas, cook for further 10 mins or so. Serve with rice, can be american long grain if basmati is too costly. Again, can be livened up even more sometimes - add a handful of spinach, serve with naan bread.