Try to avoid white flours, sugar, pasta, rice, potatoes and corn. Whole grains in small
portions are good.
For breakfast for my mom, I would saute spinach and also cherry tomatoes, make a bed of this for poached eggs. You could get some whole grain bread, like Ezekiel's or something like that an offer it.
A yogurt parfait with unsweetened yogurt and fruit would be nice for a casual breakfast with a hard boiled egg. You could do a Turkish breakfast: hot tea, sliced salami, cucumbers, tomatoes, hot hard boiled eggs, yogurt with sugar free jam, The Turks use honey and a baguette, but you could offer a slice of the bread. Omlettes would be great too for breakfast!
Lunches, why not a spring vegetable soup and a tart salad, or quiche. Whole wheat pasta might be okay, you'd have to ask her.
Dinners - I make my mom lots of meats and 2 types of vegetables, or a vegetable and a salad, and a small portion of whole grains like quinoa or farro, sometimes 1/2 a baked potato. We do roast chickens, pork tenderloins, steaks, flank steak, things like that. No one misses the carbs!
I hope this helps a little, you can do a search for foods that are low in the glycemic index and try to maximize those. Then go for a walk after each meal. I learned a lot on what to advise my mom from the folks here (thanks again!!).