Welcome to Skyrim Forums! Register now to participate using the 'Sign Up' button on the right. You may now register with your Facebook or Steam account!
You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
Well, based on what you've said, it seems the game was bugging out a little. There are times when enemies do follow you into different cells, but not very often does this happen in Skyrim, only rarely. It could have been one of those cases. Most of the time, they will not. And the follower may...
To answer your first question, I think that Serana being a child and exploring Castle Volkihar happened before she was offered to Molag Bal, meaning before she became a Daughter of Coldharbour.
I've heard a lot of theories on her age, as I have wondered about it a lot myself. I don't believe...