And if she's not, we might want to avoid developing a reputation among dangerous assassins for taking their kids. Once is an anomaly, but twice could start to look like a pattern.
We've already done it twice. No, three times. Cassandra is the daughter of
two dangerous assassins, and then there's Rose, who we admittedly didn't
steal, but still.
She's currently 16 and a half. Yes your wards are back online and the anti-bad intent ones would likely prevent a traditional trap. It wouldn't prevent something crazy like Sportsmaster sticking a bomb inside of Jade and then detonating it to kill someone (which is admittedly a little far-fetched) so a trap is still possible, it's just a question of how much Sportsmaster is willing to do to achieve his aims (which the quest-goers probably have a better grasp on than Lex).
Plus, even the average high-end individual like Sportsmaster probably still doesn't know how our wards do what they do, unless he knows about magic and maybe not even then.
My google fu fails me, whose Liselle Sloane?
Sorry, that was indirectly cruel of me. I made her up. Liselle Sloane (nee Luthor) was Leland Luthor's little sister, the WWII Mister Terrific's paternal grandmother, and Lex's great-great-great-great-aunt. She used her superpowers of getting bored easily and being very very good at nagging to battle the deadliest menaces of her time.
Specifically, she independently
rediscovered John Snow's cholera results because she was bored out of her skull from deportment lessons in the early 1860s. She then nagged her brother into putting his weight behind the construction of Metropolis' first reasonably sanitary waterworks system, and then into
building her a microbiology lab, which she made considerable use of. She escalated from there, prevailing upon family friendships to nag
President Grant into helping to organize the American Red Cross
six years ahead of schedule.
She kept SCIENCE!-ing from there.
In 1903, Mrs. Sloane (nee Luthor) received the Nobel Prize for Medicine for discovering vaccines for cholera and typhoid fever, making her the first American Nobel laureate and one of two women to win the Prize that year; the other was Marie Curie.