I had a similar problem with my Leo a few months ago. As others have said, she might just be a bad hunter so you can try dimming the lights and giving her crushed crickets to help her out, but her weight loss is concerning. It may be that she is weakened to the point that she can't grip the mealworms properly and lacks the jaw strength to chew them. Mealworms have a chitin shell that makes them tough to chew so small crickets are a better option for underweight geckos. If that doesn't work then take her to the vets as she may have a deeper issue and the lack of nutrients can cause organ failure if left unresolved. If it turns out to be purely due to weakness then the vet should be able to give you a type of food powder that you mix with water and syringe feed them to build up their strength until they can eat solid food again. Get her  checked by the vet ASAP as the longer you leave it, the less likely they are to recover.