She was 16 years old at that time so not that young. You should already have a bit of common sense with 16/17 years old. Hyunjoo could be dead by now so I can't feel sorry for the group. Her career is ruined but she can still start from zero and prove she's not a shitty person anymore (if she really changed)
But how is Hyunjoo's attempt Naeun's fault? She might be involved, but we have no idea to which extent.