IMHO there is NO way you should keep two veileds of the opposite sex together after they are about 3 months of age...no matter how large the cage is. As soon as the male is old enough, he will attempt to mate with the female. If you allow a female to become gravid (pregnant) before she's fully grown herself, you are putting calcium (and other) demands on her to make fertile eggs when she should be using the calcium and other nutrients to make her own bones/body. This is a "recipe" for health problems for the female. (And I do realize that veiled females can make/lay eggs.)
Keeping a pair together after they are a year old is adding unnecessary stress to their lives. If the female is gravid while they are together, she will have to show it to the male every time he comes near her...and they could easily fight if the male doesn't pay attention to her warnings. Do you really want either of them to be injured?
Keeping two females together (without a male around)is stressful to the females too. You may not see the signs of stress between them and just end up with one of the females going downhill and dying.
Not only should they not be sharing a cage IMHO, they should not be able to see each other from their cage. The only time they should see each other or be together is for breeding purposes.
In the wild, chameleons have the option of moving away from each other (out of each other's territories)...in captivity we don't give them that choice since they are confined to a cage.
One more thing...sinced female veileds can produce eggs at an early age without having mated, I always keep a container of washed sandbox sand in the female's cage so that she can lay eggs in it if she has eggs to lay. If you don't provide the female with a suitable place to lay the eggs, she could die eggbound.