A sob story won't make their decision to murder a ton of unrelated people redeemable.
Right now they are just as bad as that priest.
On the face of it, I agree. However, first of all they are probably still minors and thus very impressionable and possibly under a whole different set of laws. They certainly were when they were rescued, at least, making them both
Tyke-Bombs. Right now they've only made it far as "attempted terrorism". If you go back to chapter 13, it's reported that they took over the AAC without any casualties at all. Everyone evacuated safely. If (and when) the heroines succeed in stopping them, that will get them a considerably lighter sentence. Hopefully one that does not mandate interceptors. That would be the cruelest irony. That sob story was some legitimately traumatizing stuff.