Buy some flax seed. Grind in a spice grinder (you MUST grind it or they can't eat it). Gutload mealworms with this, plus a few carrots, a bit of oatmeal or bran, some calcium powder and fish food. Don't grind too much of the flax at one time, it needs to be fresh, will stay fresh in fridge but should not go longer than 5-7 days out of fridge.
In my experience geckos fed on mealies gutloaded with flax seed grow fast and get fat. The flax seed has a nutty flavor geckos love and seems to stimulate appetite, plus it is full of omega three fatty acids which are very good for your geckos. Mealies gutloaded with flax are much healthier than waxworms, and more effective, IMO.
If she is an adult you can also give her one pinky a week, that will help her too.
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Sarah Stettler
StarGecko
Starling@stargecko.com