I would love to see one or more girls getting tortured and killed by another girl, just in general. I shouldn't comment on Tasha specifically, but one point in her favor: She already got raped a lot by the guys, that's the one thing missing when a girl alone does the torturing.

If you want to add a female sadist to the group that's fine, but in that case I'd expect a grownup woman, so I assume one of the other girls will be forced to torture her, possibly as her only choice to avoid getting killed, and then probably still get killed afterwards. I think one of the older girls might work best as the torturer, one who is old enough to understand what's happening. Tricking a very young girl into doing horrible things she doesn't even understand is another option, but I think I would prefer an older girl to keep the young ones completely innocent.
Going from the interlude pictures, Molly and Miyu might prefer to torture Laurie instead. ;-)
Actually I think that might be an idea worth exploring, with a few more interlude pictures showing Laurie really annoying the two older girls, and all of that then culminating in those two girls getting the option to punish her and almost eagerly taking that chance at first, before getting horrified when it's getting much worse than they thought it would.