I had to make lunch 4 days a week also while my son went to preschool. I tried lots of things usually a few I knew he would eat with a couple that I wasn't so sure about. Your child will not starve if she doesn't eat everything.
Our pediatrician indicated that as long as my son was eating fruit and I was offering veggies that I shouldn't worry too much. Also, the doc said it was okay for my son to miss a meal once in a while if he didn't want to eat what I fixed.
With that said, I have put in his lunch the following: cold quesadillas, cold pizza, a couple of slices of salame with cheese, the baked crunch peas that go on salads, carrots, grapes, bananas, apples in all forms, pb&j, edemame, string cheese, cubed cheese, sliced cheese, crackers, jello, yogurt, gogurt, celery w/peanut butter, graham crackers (plain & with peanut butter), anything snacky that is a finger food he seems to like. I try to put the things in his lunch I know he likes.
He eats what's there, or he waits until dinner time. Same thing at dinner time, and we expect him to eat what we are eating. He has a choice within reason at snack time. We don't force him to eat, but we say, "This food is what mommy and daddy are eating. It is dinner. If you are all finished, that is fine, but no snacking after dinner."
It works for us.