A formidable OPA militant, Ostman brings Dawes to Tycho and tests whether Holden's coalition has more than rhetoric.
Aimee Ostman is an OPA leader with the unassuming appearance of a middle-grade science teacher and a history of attacks against inner-planet military targets greater than those of the other summit delegates combined. She comes to Tycho Station because Fred Johnson called her, but brings Anderson Dawes along without clearing it with the meeting's new host.
When James Holden excludes Dawes, Ostman vouches for him and reacts sourly to Holden's assertion of rules. She challenges the coalition's position, mocks its apparent pattern of losing territory, and presses Bobbie Draper on whether she represents Mars. Her questions make clear that she will not offer loyalty merely because Fred once wanted it; she needs evidence that the plan will change the balance against Marco.
An adult Belter woman with an ordinary, teacherly presentation that conceals a hard political and militant history; she wears practical civilian meeting clothes and keeps her lips pressed thin when displeased.
Ostman represents the armed OPA factions whose cooperation could strengthen the coalition but whose distrust cannot be wished away.