This character has always fascinated me, being the daughter of the series' big bad. I always wondered what happened to her after her debut. I think Joe told her about the Immortals and that combined with the fact that Horton killed her fiancé and showed no remorse for it, Lynn disowned him. That might also explain one of the reasons as to why Horton is obsessed with killing Duncan. I even think she would've been the right love interest for season 2. Think about it:
Tessa: Season 1
Lynn: Season 2
Anne: Season 3
Amanda: Season 4 and 5
Numerous (including Amanda): Season 6
Why do I think this? Well, both Duncan and Lynn's lives were ruined by Horton and the Hunters when they killed Darius and Tucker. Tessa was killed by a mugger, but that wouldn't have happened had the Hunters NOT abducted her. I feel like at some point in the season, Duncan and Lynn confide in each other over loosing their future spouses and that's when they get together. Horton can even accuse Duncan of turning Lynn against him and have Lynn help in stopping Horton for good. But she breaks up with Duncan as being with him reminded her of how Horton hurt her. That I loved that idea so much, that I incorporated it into my fanfic, Highlander: The Avenger, but have Owen be Lynn's main love interest. Hell, if they ended up using Lynn as the right love interest for season 2, and still couldn't bring Kate back for The Source, Lynn would've been a better love interest than what's-her-name.
-Roland Cain