When she was good she was very very good, when she was bad she was horrid
Agatha is the more innocent one often smiling softly and playing with her hair.
Christie is very protective of her sister and sneers a lot, seeming to giggle whenever she sees someone and pointing.
Orphaned as babies, all of their families are mysteriously been murdered and it's often how the girls drew they die. Other than that no one can find out anything about them, nothing concrete anyway. Most people just stay away from them.