Our first child ate a PB&J everyday for 6 years, with a side of apples. It was fine.

That's a really nice, balanced, healthy meal.

To me, it depends on what it's replacing. In my family, I usually make breakfast and dinner. I put a variety of things on the table, and the kids pick from amongst those things. I take into account what my kids like when I meal plan, so that I don't serve a meal that's all things that they hate, but I don't allow them to pick something that's not on the table.

By elementary school, my kids make their own lunch. They make their own after school snack, with pretty much free range in the fridge (I might say that X is off limits because I've planned a recipe that uses it). Once a week, they also plan and make dinner for the family. If my kid was eating quesadillas 3 or 7 times a week, as a snack he planned, or a meal he made for the whole family, or lunch he packed for school? I'd be fine with that, and pleased he'd found something healthy, and not too expensive. But it's unlikely that I'd serve it for dinner 3 times a week, because the rest of us enjoy variety.

If I had a kid whose diet was really limited and this was one of the few things they'd eat, I'd probably look to "chain" it to other foods. So some days, I'd put the whole meal on the table, and then other days I might put black beans with rice as a side dish with chicken (knowing the kid might not touch the chicken), or cheese quesadilla, and move towards say black bean soup and grilled cheese sandwiches. But it sounds like this is your kid's favorite meal, rather than the only meal they'll eat.

Also, not saying my way is right, just saying what I do, and what has worked well for me so far (kids are teens).

Which whole grain tortilla will she eat? My kids only want white soft tortillas