You'll need a ladder, a team and Elin's clothes to get her.

1.Go to holy get Elin's clothes and go to the well and use the rope ladder to go down.fight the three trolls and get the key.
2.Go to the locked door and use the key to open it.Fight the E.T when your done press the glass with Elin in it.

Then you get Elin ^^ good luck