My biggest tip would be make 2 portions out of everything. For example A fillet of white fish or chicken thigh, a potato(microwaved then scoop inside out and mix with a bit of butter) and spinach/ courgette etc. that would make 2 meals so she would have the 2nd portion for lunch the next day. I always give her porridge at some point in the day. If she doesn’t have it for breakfast I will give her a small porridge pouch for snack. Cooked and chopped spinach goes with everything! I add it to egg, or to meat, fish or mash etc. Courgette is an easy veg too and you get 2-3 days worth when cutting and cooking one. Broccoli and cauliflower can be bought frozen and just take out 2-4 florets out at a time and microwave then store half for the next day. Banana and blueberry pancakes, toast with cheese spread, scrambled eggs, eggy bread (dip bread in egg then fry)
Have you tried any cook books? Found them so much easier to use instead of constantly trying to think of meals especially now we’re on 3 meals a day, if not i personally would recommend What Mummy Makes on amazon x
Avocado and scrambled eggs is good, maybe try sweet potato also pasta and tomato sauce