Personally I hope they do this. For me one of the biggest draws to BG3 are the companion relationships and Minthara is such a wonderfully voiced and incredibly intricate character, but locking her away behind some non-existent "evil playthrough" is a terrible mistake.
As usual I'll draw a comparison with Star Wars KOTOR series, imagine if the devs locked Visas Marr or Juhani behind exclusively Dark Side choices... we'd entirely miss out on such intricately written characters and more importantly their fascinating redemption arcs.
So if not with any elaborate dialogues, then at least making Minthara a special exception to the knock out rule would be enough, so that she actually continues to exist in the world and we find her in ACT 2 once again.
BG3 doesn't have an "evil playthrough" as none of the choices lock the player into any "evil paths" that are not available otherwise. There's just one bad choice that locks away Minthara and that's it, the rest of the game plays exactly the same for both good or evil characters. With plenty of variable nuance naturally, but in Minthara's case there is no nuance. It's either live or die.