What the hell are you blaming Jee-han for? He didn't bring her into that labyrinth, nor does he know a way to prevent her from suddenly re-appearing in it later. Her circumstances are not his fault; rather, he is giving her a way to survive.
Certainly her getting dragged to the Labyrinth is not his fault.
But, by exposing her to his abilities, it will alter her from normal human into someone that is affected by that world's system (by Gaia or something)
Thus exposing her to more danger like becoming Mana Source by those Black Market.
AND, he isn't giving her a way to survive, he is only giving temporal solution. Once she enter that world she will need to get stronger to protect herself, no way getting back to her normal life.
It does not matter anyway. One way or another she would die. And since there are a lot of weak people aside from her, i do not think its safer to not teach her anything and let her die the next time she gets sucked in.
NOOO STOPP
DONT DRAG CLASS PRES TO THE ABYSS SIDE OMG
JEE-HAN U BAKAA
Im sure he gonna get scold later.. either by loli masta or shinsunil