Is it bad to let my little sister tan?

my mom put me in charge of our at home tanning beds (we have 2) and my littl sister maddie really wants me to let her tann for her birthday next week. she will be 9 years old. and is it unsafe? shes tanned before for beauty pagents but we made her stop cuzz she was only 6 7 or 8. but i started tanning when i was 9 and so did all my oth sisters so should i?? cuz she says its unair but shes kinda right i think.