Mother is 98, advanced alzheimers, lives at home with me and my husband. She can't understand time. We have tried to schedule our meals at around 8 am, noon and 5 pm. She is good about breakfast, between 8 & 8:30. Then she out again around 10 wanting to eat, we give her coffee and cookies. Lunch at 12 or so. But about 2:30 - 3:00 she's out wanting supper, not a snack she wants a full meal. This will continue every 10 - 15 minutes. Until one of us becomes irritated. She sometimes becomes threatening. Mother goes to bed after supper and eating early throws her off. She eats well. We like to have a cooked supper.
Since time concepts are not very meaningful to Mother, there must be something else sending her looking for a meal so consistently in mid afternoon. If you prepare her a full meal, does she eat it, and then also eat her supper? What about saving a serving of tonight's meal and giving it to her at 2:30 tomorrow? If she is not so hungry for supper later, perhaps she could have a lighter portion or a snack while you have your meal.
I'm trying to think of ways you could give her what she wants without undue extra work for you. A microwaved frozen meal might work mid-afternoon, too.
In my mother's family, the 4 meals of the day were breakfast (substantial, after milking and other chores), dinner (again substantial, often with many field hands sharing the table), lunch (a lighter meal of sandwiches, cheese, pickles, cake, coffee and lemondade, carried to the workers in the field and eaten sitting on the hay wagon) and finally supper (a lighter meal for just the family). I remember a conversation with my aunt, in her 90s, with her saying she knew she didn't really need 4 meals anymore -- she wasn't doing farm work -- but she always felt like she had to have her lunch in the afternoon.
If you can figue out how to satisfy Mother's need for her afternoon meal, keep her up for a lighter snack at supper time, and get her off to bed, you'll probably all be happier.