They are able to produce eggs, even without mating, from the age of about 5-6 months (some keepers have reported earlier ages). So it is important that you monitor your chameleon for any changes in colouring, weight or eating habits. If she does produce a clutch, she will need somewhere appropriate to lay the eggs, otherwise she may become eggbound and die.
Dave Weldon has posted pics of his egg laying bin - do a search for it on the forums.
If possible however, you want to try and prevent them from developing any eggs at all (at least until you're ready to actually mate them and have them breed - and you wouldn't want to do that until the female cham is fully developed at about a year old).
It is thought that overfeeding can trigger them to develop eggs whether they have been mated or not (leading to the production of infertile clutches). It is possible that warmer temperatures might trigger this too.
Kinyonga often mentions that she has been able to successfully prevent her Veiled and Panther females from producing any infertile clutches by controlling their food intake and basking temps.
As to what exactly constitutes enough food, and what constitutes too much, that differs for each cham (based on different levels of activity, ambient temperatures, calorie count of feeders used, etc). It may take some experience before you work out how much to feed.
My first female is 13 months old now, and hasn't produced any eggs. She has a voracious appetite, but I try to feed her sparingly, though regularly (she eats more frequently than my male did at her age).
