Hello!
Your chameleon girl is growing and maturing, and that's very cool, it means everything is going as it should.
First of all there is a great educational video about setting up a laying bin made by one of the forum members. You can find it here:
https://www.chameleonforums.com/laying-bin-set-up-educational-video-77225/
As you were already told - females can and will lay eggs even though they have never been with a male, then the eggs are just gonna be infertile and you can simply discard them.
Making and laying eggs puts a big stress on females body, that is why it is advised to keep females on a stricter diet and at lower temperatures than males. By doing that you can reduce the clutch size, and, in some cases, keep her from forming and laying eggs at all, which will among other things quite likely prolong her lifetime.
It is extremely important to supplement the pregnant female with plenty of calcium. Calcium is required to form eggs, and since reproduction is always a priority, in case of lacking calcium, her body will pull it from her bones, which can lead to metabolic bone disease (known as MBD). Calcium is also essential for proper muscle functioning and other bodily functions, so supplementation is very important. You might want to buy some liquid calcium and either give her a drop directly or put a drop on one of her feeder once in a while. It is also advised to give her some liquid calcium once she is done laying eggs.
Females usually change coloration once they become gravid. I don't have any photos at hand, but I am sure if you make a search on the forums for a gravid female you will be able to find some examples. However! some females only do that if they have been mated and their eggs are fertile, but remain the same color if their eggs are infertile. In that case you might still guess that she is developing eggs from her becoming more plump and putting on weight even though you feed her the same amount of food.
Finally, it is very important to give her privacy, when she finally starts digging, otherwise she might become stressed and become egg-bound. Some choose to cover the cage with a cloth during the process.
Sorry, it turned out so long, but I hope this helps you to get a better idea of how to give her the best care in this important time. If you are in any doubt - just ask.
Best of luck to you and your cham,
Julija