Hey Colleen. If you haven't read it yet there is a
Leopard Gecko Care Recommendations in a Nutshell put together by Elizabeth. It is definitely a recommended read. As well Ethan posted a link to the
Pros and Con's of Meal Worms. Another good read when it comes to picking food for you're leo.
Aspen bedding, being wood shavings, tends to hold on to moisture and bacteria. The leopard geckos natural environment is rocky, hard pack clays in the middle east (Pakistan, Afghanistan, etc). They really aren't made to move around in loose substrate like wood shavings, cocao fiber or sand. As well an excess of humidity can cause respiratory issues in leopard geckos. As panthergecko mentioned, it's suggested that you use a substrate like stone (slate) tile, paper towel or
reptile carpet. Again there is a whole discussion regarding the substrates people use. I believe it's somewhere around 50 pages now :roll:. Before you start getting concerned about impaction I would suggest changing out the substrate in the tank and keep an eye on her. Geckos will usually use the same area as a bathroom all the time so finding it after changing the tank wouldn't be an issue.
And as a correction, a body needs calcium to digest phosphorus. If there is too much phosphorus to the amount of calcium present in the food they eat, the body will leach calcium from other areas available. Over time this can lead to MBD (metabolic bone disease) that causes weak, spongy bones that break easily. Think of it like osteoporosis. This isn't unique to reptiles, people can get MBD as well, it's just captive reptiles are more prone to due to the available food.