Sure but you infantilize them. Are they not accountable for their acts? Then they should still be under care and not having voting rights among other things. Do you think the same about male teens?
For instance if Ivy tells Holly to kill somebody, it's Ivy's fault and not hers?
As I mentioned a few times, the responsibility falls two both. There is the drug distributer and the one accepting the drugs, there is the abuser and the one who allows themselves to be abused (assuming they are in a position where they can easily avoid the other person).
Holly is noticable underprepared in Ivys world, Lena has constantly to interfer and assure her or stray her off. This works gameplaywise to control Hollys fate, but as a result, Holly comes off as very codependent and weak-willed, so I ascertain that Lena and Ivy influence her beyond whats acceptable in the worst routes.
If its clear that Ivy's killing order is a joke, then its on Holly. Else, Ivy can be charged with incitement/soliciting of murder, so they get charged both. Depends on the circumstances, obviously.