Additionally, I have an adult female housed temporarily in a 40gal aquarium, 36x16x18 inches and it's honestly way too big for her. She's about 3000grams and roughly 4.5ft. Most of my adults are in 41qt sterilite tubs and quite happy with the space, roughly 36x16x6 inches in dimension.
Floor space is more important than height since they spend most of their time on the ground but they arent very active and usually prefer to chill out in their hides so they actually don't need alot of space to move around in. Extra space is generally wasted with them since they dont use it much.
Whatever size you end up with, maybe in the meantime while she is growing you can like make a divider to block of some of the space and keep her habitable space small and proportionate to her size and just move it as she is growing? I had a wooden divider similar in one of my bigger tanks seperating it into 2 and worked great.