Honestly I feel both sad and disappointed at the 2nd disciple. Like, something Obviously ...

I think that she was just so desperate to have someone to fill the role of “Master” in her heart she didn’t necessarily care about what they did or who they were

I think she tried to bring her master back from the “dead” but the spell backfired and hurt her itself, that’s why the forest was damaged so severely. And she lost her memory and somehow believed that man is her master now