An aquarium is not a great home for most chameleon species. Unless your veiled is very young, it probably isn't a great home for her right now. A veiled really needs to be kept in a screened cage. That way, the cage gets air exchange and bacteria doesn't grow as easily. Chameleons are susceptible to upper respiratory infections, and one of the main causes is a lack of ventilation. Plus, some chameleons get stressed over their own reflections. An aquarium is really hard to offer a heat gradient in also. The basking light tends to heat the entire thing to the same temp, usually very warm. A 36" tall screened cage is a good size for a female veiled, but she would probably like a taller one even more. If money is a concern, reptariums are inexpensive and lots of folks like them.
Heika