Youth Won!

Not to refute your conclusion, but Cinder let go before Vernal died, since Vernal later got up and shot her in the back before finally breathing her last.

You’re right she did do that, but Cinder THOUGHT she was dead. She thought that she’d done what she needed to do, THEN looked at her hands like “wait where is it?” She didn’t LET GO until the moment she thought Vernal was dead

We’ve seen the transfer start immediately from the moment Cinder latches onto someone though. She began stealing both Raven and Penny’s powers immediately. I think Cinder was just so caught up in gloating that it didn’t register for a second that nothing was actually happening with Vernal. That being said, I agree with you on death being necessary for the transfer with the arm. Given that the arm hasn’t shown to allow a successful partial transfer like the Grimm bug, it’s either that she didn’t latch on for long enough with Penny or Raven or that she does need to have the maiden impaled on her hand at time of death for the transfer to finalize (which is super fucked up lol)