i make a lot of meals from scratch and enjoy making all of the following:
sausage casserole, chili con carne (you can use same ingredients as spag bol, then chuck some chilli powder in for very simple change to your monday dish!), corned beef and potato pie, lasagne, potato gratin, bubble and squeak (from any left over veges), indian curry, thai green curry, fajitas,
most of the above use same veg e.g onions, garlic, peppers, mushrooms, courgettes, potatos so you can buy job lots from supermarkets and have very little wastage.
why not offer to cook something one night to give her an evening off, then you can cook anything you fancy!