She is roughly 12 inches from beak to tail. 9.5 lbs. Please let me know if there is a more formal method of recording tortoise measurements and I will gladly report back.
It is usually measured in SCL or straight carapace length. This is the straight line measurement from one end of the shell to the other, front to back. You can place the tortoise next to a ruler and use that, or put her up against a wall with a ruler if that is easier. Hope this is clear enough, someone else may be able to give you a better explanation.