She's a gorgeous little gal! They grow like weeds don't they? As a female, she'll probably top out at 7 to 8 feet. Then she'll grow very very slowly for the remainder of her life span.
Check out AP cages. We have 3 and they are phenomenal. Solid, affordable, aesthetically pleasing, and great for holding humidity. Also really easy to assemble. There's a pretty long wait time, 10 to 12 weeks, but if you can work around it they are totally worth it!
We got a T13 for one of our girls. Even if it looks huge for them when they're young, boas aren't agoraphobic like some other commonly kept snake species. Starting with a larger enclosure can help to save money in the long run, instead of constantly upgrading to larger enclosures, and stressing your snake with frequent moves. The PVC enclosures definitely seem to make our snakes feel more secure as well, since they aren't surrounded by glass on all sides.
Awesome. The t13 is on sale now. Thats a good price for a cage. How does it hold humidity and heat. The glass tank i have now is such a pain to stabilize