Female veileds can/do lay eggs even when they have not been mated. They need a place that they are satisfied with to dig to lay the eggs in or they will not lay the eggs and can become eggbound. Signs that they are going to lay eggs are increased width, especially closer to the back legs, not eating as much as usual or not eating at all, drinking more than normal, roaming the cage (especially the floor)....and of course, digging.
I do not use a substrate in any of my chameleon cages because it can be ingested (either accidentally or on purpose) and many of the things that are used for substrates either cause impaction/blockage of the intestines or contain something toxic. (I also cover the soil of any plants that are in the cage so that she can't ingest that.) I put a container of washed sandbox sand in with every egglaying female and leave it there always so that she has some place to dig when ready to lay eggs. The container needs to be at least 9 or 10 inches deep and longer and wider than the chameleon by several inches (tail not included). The sand needs to be moist enough that it can hold a tunnel so that she can dig a hole.
Veileds will often dig for several days and even dig holes in several different places looking for a site that she feels is appropriate. She should decide on one hole eventually and dig that one deep enough to lay eggs in. Don't let her see you watching her when she is digging the hole or she might abandon the hole. If she abandons it often enough, she could become eggbound. She should turn around with her nose pointing out of the hole and sit there when she is ready to lay her eggs. Let her lay them and completely bury them....then they can be dug up.
As for the sleeping, they usually choose one spot and sleep there every night. Some of them are heavy sleepers and will not appear to breath.
To keep a chameleon in captivity so that it will be healthy and live a long life is not an easy thing. The husbandry (way you set up the cage, feed and look after it) needs to be good/right or the chameleon can end up with health issues. Temperature, gutloading the insects, supplementation, hydration are all important. Veileds are omnivores once they reach about 6 months of age and will eat the plants and greens, fruits and veggies in addition to insects.
If you would like to know more, I will answer any questions that I can. I have kept chameleons for many years...and most of my veileds now live for over 7 years, reproduce and produce healthy babies.
In the meantime, here are some sites that have very good information. The first one has some good articles on vitamins D3, calcium and vitamin A, etc. that give important information.
http://www.chameleonjournals.com/vet/
http://adcham.com/
http://www.chameleonnews.com/index.html
I hope that she will get through this egglaying and continue in good health for you for many years!