Its a catch 22 situation...if you don't leave a container of sand in there, your chameleon could die eggbound if you don't know when she is going to lay the eggs and move her to a container...and if you leave it in there she will continue to the sand...but the sand eating is only a bad thing IMHO if it is likely to cause a blockage. If the sand is passing through her, then hopefully it won't cause an impaction.
Mine have eaten the sand for years and I've never had an issue with it.