Wow, no nightcrawlers, huh? That's a shock. Many of my turtles won't take European red wigglers, but they go bonkers for nightcrawlers...all of them.
Good news, superworms are a great food item for a turtle! If she eats them, you can accomplish a favorable Ca
ratio simply by dusting them before feeding about once weekly. Luckily, the Ca
ratio is much less critical in adult turtles. You are right to be thinking about it, though. It can certainly affect breeding and also overall health in extreme cases.
Supplemented superworms and crickets, combined with whatever fruit matter she will take is actually not a terrible staple diet for a Florida box turtle. If you gut load the insects with greens as well as weekly dusting, the turtle should thrive. It will, however, cost more money in the long run. Your best option at this point seems to be fortifying what she will eat and encouraging her to take additional items. You can feed her in the same manner every time in order to get her conditioned. Then, she may learn to immediately take whatever you offer in that same manner. No matter how picky my aquatics are, if I offer something to them from forceps, they take it without question. It takes me roughly six months to train them as hatchlings, but it is worth it.
My Florida box turtles are all captive produced, but it has still been difficult for me to get them to take anything but living prey or meat due to their carnivorous nature. Here are some items that mine relish...
Whole minnows, skinned mice, raw chicken breast, chicken livers/gizzards/hearts, beef heart/kidney/liver, shrimp, and crayfish.
Cooked sweet potatoes, tomoatoes, cucumbers (sweet ones, not bitter ones), cooked carrots, peas, and fresh green beans.
Some of my box turtles won't take plain reptomin or other prepared foods. But, I've noticed that if I soften it and combine it in a 1:1 ratio with some type of vegetable, especially cooked sweet potatoes, they go crazy for it! Softened reptomin and mazuri aquatic turtle food have been fantastic for allowing me to "sneak" non-preferred food items into my turtles' diets.
Sorry for the long post. Hope it helps.