I think the two things are probably unrelated.
The bugs are most likely to have come in on the crickets (or whatever other insects you are feeding), or on any live plants you might have in the vivarium. Also, crickets have a tendency to pump out offspring whenever it’s warm and moist – they can look a little bit like tiny bugs.
Be careful how much you take her in and out for cleaning, it can cause stress, which isn’t going to help with appetite.
When I had a leopard gecko as a youngster, it wasn’t unusual for him to lose weight every now and then, for no apparent reason. The only “link” I could ever find was it seemed to coincide with when he accidentally ate the substrate. What do you have down in the vivarium? She may have eaten some of that and it’s causing a loss of appetite.
ALso, have you tried changing diet? maybe try some mealworms if you don’t already vary the diet.