First of all, I've never cooked cheese on toast in my life. I imagine I could figure it out, but frankly I detest using the grill so the likelihood of me making it is zero. Not to mention that I can't eat the bread, ds1 won't eat the cheese, and ds2 wouldn't eat it (ex made it once and ds2 refused to eat it). So I can't say the lack of cheese on toast is an issue in our house. 
Secondly, I actually can cook and bake a wide variety of things, but I can sometimes go awhile without cooking. Not a long time, but a couple days here and there. My children are well fed and eat mostly healthy food (although we'll ignore those smarties they had from the elf this morning). We don't cook very much in the summer either.
The OP states that the woman heats up food left by her DW in the microwave, so clearly she is capable of some cooking (or heating up of food).
And if she doesn't do any cooking, so what? There's loads of things you can make without actually cooking, plus you add in meals at restaurants, maybe a family meal at a parent's house once a week, they probably have hot meals at school every day.
And FFS no, do NOT get her a cookbook for Christmas.
So much for tolerance and support. "MN - by parents for parents... unless you can't cook, in which case we'll set on you like a bloody pack of hyenas." Sounds about right. 