I'm not sure if Minthara on a good path can be the same Minthara of house Baenre that you recruit on the evil path.
What are you even saying? It's not like she would change if you recruit her a different way lol.
Wyll and Karlagh leave you when you massacre the grove. This makes sense.
Minthara is the mirror image. But you want her to join while massacring her goblin army. (There can be a rationale for her betraying the absolute, given her backstory, which you learn when you recruit her the evil way.) But betraying the absolute wouldn't change her own upbringing, ambition and philosphy of life, so to speak.
So after recruiting her, I suppopse you will continue being a good person throughout the rest of the adventure, with a Minthara companion who will disapprove of your decisions 90% of the time, but still you want to keep her. It makes no sense really, unless she changes character so she approves the good things you do. So, it seems you don't want Minthara of Baenre, but just a good Drow Palladin who is ready to forsake her heritage.
You already turn Lae'zel like this, but Lae'zel is young and hasn't started her fighting career yet in earnest. Minthara is already a leader when you meet her. So it's not quite the same.
Anyway, these are just some thoughts. With crafty scenario writing, I'm sure a turning-to-good story can be made. I 'm still not sure it will be satisfying in the end. Isn't the real challenge to find out what the real Minthara is like, and walk in her shoes for a few miles ?