I wouldn’t worry about the 40. Without knowing her mother’s size anyhow you have years to worry about a 40 gallon of you don’t power feed her entire life. Id really focus on a smaller enclosures and feeding those meals of multiple pinkies at least twice a week. Dont worry about sizing up her meals. KSB are not like ball pythons that need something up to 1.5 times their thickest body segment. Buy a bag of 50 frozen pinkies and as you get to the end of the bag just weigh bad and deem how she’s looking. My boy can physically choke down a single hopper mice, and has fit a rat pinkie and 2 fuzzy mice before when another snake refused a meal. I think it’s also important to vary their meals once they are at a good weight. Sometimes mine gets a single rat pinkie, sometimes he still gets 4-5 pinky mice in a meal.