my chameleon is pretty thin, but she has good energy + stamina, is a good eater (she loves her treats ) and everything. should i just give her more fatty foods/treats to fatten her up a bit?
She looks perfect! You want to avoid fattening up females, unless it's medically necessary. When you over feed females it makes them produce a bigger clutch of eggs and more frequent lays.
I am not sure how old she is but she looks perfectly healthy. Ditto on want @ehdee6 said above... Here is female specific info.
Females:
As she matures you will have to start cutting back her food. By about 6-7 months she should be getting about 5-8 small feeders each day. At about 7-8 months you want to slowly reduce by cutting down feeder amounts so that she is on a feeding schedule of 3 days a week with 3 feeders. You want them to be on this schedule by the time they are 9-10 months old.
You will not ever want basking to be over 78-80 for her. The hotter the temp the more their metabolism speeds up so we have to keep the temp lower since we are doing lower food intake.