Whoa, I'm genuinely pleasantly surprised to see Bella actually being treated as a real person with her own feelings and motivations and not just some 1-dimensional evil child antagonist like I'm so tired of seeing in rofans.
She's only a kid, and just because her mom is greedy doesn't necessarily mean she's inherently evil or malicious. At the same time, even if her mom is a bad person, that's still her mom, so it only makes sense that she would be willing to sacrifice the life of a slime in order to save her own mother. It's not like she wanted to hurt Irina, in fact she wanted to help her, but in this world people kill monsters all the time, so if anything it wouldn't make much sense for Bella to let her mom be imprisoned and possibly die just to save the life of a single monster.
It's nice for a change to have a female character who isn't either an antagonist who's evil for the sake of being evil or some fawning sycophant who worships the ground the FL walks on.