K.B.
I would suggest putting slide bolts on very high up where you can barely reach them. I would also suggest putting two gates on her door, one on top of the other, or in the hall the same way. Put a lock on the outside of her door, a hook lock or slide bolt. I've known some triplet parents who installed a storm door outside their kids room where it latched/locked from the outside where the kids couldn't reach it.
K. B
mom to 5 including triplets