Parson initially hated Maggie because she was responsible for Misty's death. Since then he seems to have forgiven her. Their relationship began very formally but the two began to be social once Parson stepped down from Chief Warlord, to the point she feels comfortable questioning him, advising him, and teasing him about romantic and sexual matters, and has even been hinting at a level of romantic interest herself. Parson for his part enjoys conversations with her, since she is good at finding ways to "kick his ass with one sentence", making her a fun challenge to contend with.
Maggie is probably the staunchest defender of Parson's abilities post volcano-TPK, to the point that she directly argued against Stanley's order regarding his demotion. She felt that Parson was wasting his talents just acting as regent to a city and urged him to do more. When the Siege of Spacerock went disastrously wrong and Ansom went down as Gobwin Knob's Chief Warlord, she even went so far as to use a suggestion spell to make Stanley appoint Parson as Ansom's replacement. This causes Parson to feel a great deal of animosity towards her, since she made him Chief Warlord against his will. He becomes especially angry when he learns that it wasn't just for the good of the side, but an underhanded part of her efforts to advance the interests of her fellow Thinkamancers.
Parson has considered Maggie to be one of the very few people he trusts. But with recent events, he has found himself questioning her Loyalty between himself and the Great Minds. In response, Maggie has offered him the reassurance, that as long as he opposes Charlie, he can count her on his side.