it can happen, but its not particularly common. and although females kept together will get eggy if well fed, they do not usually get to a severe condition, unless put with a male. if you are particularly worried about it, then things like reducing amounts fed, or only feeding on alternate days, should help prevent them egging up in the first place. but i have one girl who has looked massively eggy for ages! and she is fine (though i might try and breed her again soon, seeing as she is so ready for it)