Minthara has the best dialogue and voice acting in the game, but she lacks companion quests and the depth of content. You can recruit Jaheira and Minsc with her, they're dependent on your choice about the Nightsong in act 2, nothing to do with act 1 choice. Also you can romance Shadowheart with her in the party if you want, I'm guessing that is act 2 based as well? Massacring the druids/teeflings has surprising little effect on the story actually.
Isabelle is a companion?
Minthara is the best character and she NEEDS to be recruitable if you side with the grove! Also- I support the important thread in the suggestions: Let everyone in the Party Speak
