Who knows ???
I am not saying anyone is right or wrong, but ... my experience with veileds has taught me not to guess ages with any amount of certainty.
I have seen 4 and 5 month old babies that look like they are 6 weeks old and then (for comparison) some of Juli's 5 month olds, which are monsters.
It all depends on the animal, it's living conditions early on and how much it has had to compete for food.
Unless you know the hatch date, you really don't know how old your chameleon is, certainly not by measuring it.
Regardless of her exact age .... she is a very nice looking girl.
My females snout to vent is 5" and to tip of tail is 11"+ They kept moving their tail so it could be a bit longer. They are both adults 13 and 14 and 15 months old.