Well, I keep a separate ofline tree for each of the spouses of my ancestral surnames of my parents, i.e. the Millers and the Dardingers As far as WikiTree goes, it's just like any other profile. Put in her parents, grandparents, etc. There's no reason to keep her separate or duplicate her since the goal of WikiTree is to connect all the world's people into one tree. Now if there's someone from her family who is interested in genealogy you might want to recruit that person to join WikiTree and handle her genealogy or at least help with it. In my Wife's Otto (father) and Ray (Mother) trees there are people on both trees who have done a lot of work, so I don't worry as much about working on all lines. Your milage may vary.
