Im with Jannb - first suggestion is to not offer waxworms (low nutritional value, high fat) unless you are needing to fatten her up after an illness or similar.
secondly, if she's not eating them up quickly, its possible she is not all that hungry (and all the more reason not to offer fatty food).
another idea is to use a large glazed ceramic bowl - I find this gives less opportunity for crawling larva to get away than a "cup" sized plastic container. The previously suggested olive oil on top inch of rim is helpful also.