I'm having trouble with an unexpected voyage. When i lead Selene down to the door she won't go into the area. I've done this quest over ten times and never had any trouble. Please Help!

reload an earlier save?

Make sure you've exhausted ALL of the conversational choices with Ormil. I don't remember the details, but there are two different new topics he has when you talk to him after Selene surrenders, and whichever one you choose, he'll break off conversation at the end of it. But only one of them triggers Selene following you, so if you pick the other one, he'll break off the conversation but then she won't follow. So you have to restart the conversation to pick the other one to get her to follow.

If that's not it, my guess would be just a path problem, and I find the best way to get around them is to just get behind the NPC and push until you get them back on the path. I have to do that fairly regularly with Guilbert Jemane to get him close enough to Reynald to trigger their reunion.

Selene is following me now but when we go to the lowest level she won't go into the door that makes the quest update pop up.

Since she is following you, and assuming that that means that she goes at least part way if not all the way down to the lowest level, I'd try just pushing her. As I recall, you get the door opening sound effect, but that door doesn't actually open and close-- she just vanishes. So there has to be a spot on the floor that's the trigger, and you just have to get her to that spot. Push her around and see if that does it.

Beyond that, all I could guess is some sort of real glitch, which will require a reload from an earlier save.

or you could kill her.

Selene can surrender? she's never surrendered to me and i always have to kill her

She sure can, but its only one specific outcome to the question and answere session she initiates when you confront her - basically you have to amaze her with your apparent knowledge of her plan and intentions - make the wrong answere choices and she'll assume your lying and attack. I can't be more specific without spoiling the event for you............

This is it. If you listen to the conversations of all the people, you will find clues as to what your answers should be.