Depends on what point of the egg development she is at. If you can see the egg bumps on her, she is probably too far along.
Using chickens as an analogous species, fertilization occurs in the first part of egg development. Sperm fertilize the egg (actual egg, not the casing we know as eggs) in the infidibulum and then a list of other processes help develop the egg, finalizing with the shell.
If chameleons are the same, which I suspect high similarities, I dont think you'll have viable eggs if you mate them now. The female will probably agree, rejecting the male.