Someone recruited both Minthara and Halsin on Reddit and provided step-by-step approach. Minthara seems to have less content than every other companion though.
I've found that she has quite a bit of content, no quests or even an entry in the companions section of the journal, but she seems to have as much if not more dialogue interjections and camp discussions, Her dialogue and VA is all exceptional which is largely why I would like to see her expanded, put in conflict/contact with more companion and made part of more varieties of playthrough.
Especially as after you get her, you can good or evil ending of every act after then regardless of what you did in act 1 so she already has responding to 'good guy' content.
Having her have to deal with working with Halsin, Karlach and Wyll would expand their characters as well as hers so it's win all round. Good characters would understand she did the act 1 things under mind control, but also see that she's only 'on your side' to protect herself from said mind control returning so there'd be drama and tense co-operation that'd make for great banter!
And @1varangian her perspective is a good take on evil, she's not serving the cult, she's after power and vengeance on the cult, and willing to do anything to achieve those ends, from putting slugs in your head to killing all the slugs. After 'good' actions she will question your motives and if you explain you did it for selfish reasons or to advance quest she is happy, often you don't have to she's just happy with things many games would say evil characters dislike because she is pragmaetic enough for that. I am happy with the approach the writers have taken in her interjections and approval effects in representing a pragmatically power hungry a neutral evil character.
Also this thread got moved from suggestions to Story & Characters
Which I guess checks out, but it was intended as a suggestion for an improvement/change in the game, not a discussion on the character. I don't know whether that should be taken as sign policy says no suggestions on story/character changes only mechanics will be changed based on feedback?