Ok, so yes, there is quite a lot of things that need to be corrected from just the little information I asked. Unfortunately, yours is not an uncommon story. There is a huge amount of outdated and just incorrect info out there on chameleons and no way to know what is right or not. There are even many exotics veterinarians who don’t have the right knowledge about keeping chameleons. They are more unique than most think. You have been doing all that you believed was perfect for your sweet little lady, so no need to beat yourself up. Let’s instead move forward and work on making the needed corrections.

Get yourself a drink and get comfy - I talk a lot.

Because of that, I’ll break this into a few different posts.
I’m not sure what to do about her eating the lay bin substrate. Usually we think they eat substrate due to nutrient deficiency. She has been getting too much vitamin D3 and multivitamins, so let me call in
@kinyonga who has a wealth of experience and knowledge and can better advise about this, Play sand, either by itself or mixed with no more than 50% organic soil is the preferred lay bin substrate. I do believe that if those two substrates are ingested, while not ideal, they are able to pass thru the digestive system in small quantities.
Your lay bin is much too small. Chameleons seem to prefer at least a 12” long and wide bin that is filled to at least 5-6” deep. One of my girls also prefers to have a tall opaque bin, so that she is more hidden in the bottom of it.
Once she enters the bin or starts digging wherever she has chosen, she needs to have total privacy. If she sees anyone or doesn’t feel safe enough, she will stop digging and can become eggbound. There is only a certain amount of time that she has the urge to dig and lay. You need to get her the bigger bin in there immediately and then cover up the lower part of her enclosure so she can’t see anyone. You can poke some small peek holes in the covering to monitor her, but do NOT let her see you or anyone. It is
priority that she lays her eggs. If she isn’t able, she will need a vet who is experienced with chameleons. She may need surgery to remove them, which would also in effect spay her. This is very risky, especially if she has been weakened. Again,
@kinyonga is better than I to advise.
More to come…..