I am playing a Fighter, running solo. I haven't invited any of the companions to my camp. Shadowheart randomly appeared one day with standard dialogue when talking to her. I have progressed the majority of the journal entries in the overworld with the exception of Auntie Ethel (I prefer her as in town vendor), so I journeyed into the Spider Lair. The day I entered the Lair, there was no Shadowheart at camp, but after I defeated the spider matriarch and ended the day, Shadowheart appeared the following morning. No idea why - not game breaking in any way, simply a surprise.
