Selene don't know what she was doing to say she even knew what's going on isn't overestimation of her abilities and skill sets Selene is a mage through and through and not just that I mage specialized in combat in simple words , investigation wasn't so strong suit or her special seat the extent of investigation was scales is tracking down a person which is useful but not in this specific circumstance

So when Selene what's given the choice between going to the school or house she really didn't know the difference 

After all Selene is many things subtle is not one of them so the moment everyone to paying attention to her she set climbing the building looking for the child to room

Selene was honestly more curious and seeing the child than anything despite her earlier words claiming that she did not have to kill a child
Isn't completely true In complete honesty this was a request of her cousin because of an incident in her childhood her cousin desperate wish for her to not need to hurt in the child

But facing the current situation Selene, what potentially could turn a child into a flash of abomination, will she be the only person in the immediate area who could solve the problem like killing the creature She really can't imagine herself, particularly caring.

But that was after all the point of this vacation See if you could find a way what's to care about humanity