It can really depend on the dragon, but 40-50 in a day doesn't seem completely out of bounds for that age. The most common rule of thumb I've seen for juveniles that are still growing would be as many as they can eat in a 15 minute feeding time. I always just did however many until he stopped, I didn't really worry too much about timing it. They do need the protein and fat while they are growing so don't be too concerned about overfeeding at this stage. Once she gets to be about a year old and the growth slows down you can start cutting back to once a day or every other day for bugs. Once she is full grown by about 18 months old, you can do bugs 2-3 times a week. The only concern I would have with using only dubias would be that they do store their uric acid and can pass it to the dragon, potentially leading to gout. This can be mitigated by feeding your roaches a low protein diet (no commercial roach or cricket chow) and adding some variety with different bugs like silkworms, black soldier fly larvae, superworms, hornworms, crickets, etc. The black soldier fly larvae are great at her age because they don't need to be dusted. They are a little small to be cost effective for adults, but for babies and juvies they are awesome as a staple. They work pretty well as a salad lure too. Sprinkle some on her salad in front of her and see if it entices her to try it out.