I hope your able to talk your sister out of a sav. I have an 8" that is approx 2 months old and just the fact the it feels the need to kill it's insects by smashing them on every hard surface in his cage before it will eat it says to me that it would be too strong for a child. An full grown sav could seriously injure an adult, I scared of what a 4 footer would do to a toddler if it felt threatened or annoyed. Don't get me wrong, they're a great animal and I love mine but they cost huge amounts to maintain and are def. not for most people.