I agree with the others. Buy a small cage for now and if you want to build something later she will need a big cage by 6 or 7 months old. Here's a cage that I built for my adult female veiled awhile back. The cost was about $100.00...
I made an inline water heater from a Bunn Coffee maker
Link to the heater that I made a couple years back and it's still working great.
https://www.chameleonforums.com/misting-system-heater-29698/
Welcome to the forums. Before you buy your chameleon test out your set up and make sure you have the heat and humidity correct before putting a cham in there.
I would recommend buying from a member here in the classified section.
Here's a link to pictures of my female veileds enclosure...