Its not selfish Rolande, it's totally human
If you're able to do some cooking, that's great as your body will need as much nutrient as it can get, grieving is exhausting for our bodies. Some foods in particular can help our minds, omega 3 has been found to help with anxiety, depression and stress, so whilst it can't make everything better a little bit in your diet can only be a good thing.
Maybe when you feel up to it try cooking different things, so it feels less routine?
Sending a big hug to you all xx