The problem I am having is that I used Mjoll at 2 different houses and can't get the steward dialog to show up. Did you do something special to get the dialog for Brelyna Marion? Or did it just pop when you went to the property?
I picked her up as a follower. I then went to my house and talked to her. The dialog was at the bottom. I think I almost missed it.
One other thing, when you use one of these for stewards and want to change there armor/ weapons just ask them to follow you. Then ask to "give items", then tell them "its time to part way."
They will say they are going back to house if you need them.