To ensure the game recognizes Minthara as recruitable later, you must make her rather than permanently hostile.
Once you have successfully escorted her past the Moonrise gates, she will thank you and head to your camp. At this point, you can speak to her and officially ask her to join your party. Why Recruit Minthara? zmsfm minthara free
Intervene. You can either fight the guards or use Deception/Persuasion to convince them to let you handle her. To ensure the game recognizes Minthara as recruitable
Enter the main throne room. You will witness a cutscene where Ketheric Thorm judges Minthara for her failure at the Grove. zmsfm minthara free
Regardless of your dialogue choices, she will be sent to the dungeons.