Also, Wyll and Karlach are still complete buffoons for leaving you in evil path - w/o Prism they'd mindflayer themselves.
So, didn't see before you complain about why the game don't allow you to make Karlach and Wyll as evil companions and keep them by side even after raid.
Because I prefer "Good" runs and this a thread about Minthara specifically. Simple as.
If you wanna my take, sure: they should either be still pressured into following you due to a bigger picture (opportunity to infiltrate the cult + them not surviving outside Prism's area of effect) or, them leaving you due to raid in Act 1 only to be prisoners (who can be rescued) in Act 2 at Moonrise similar to Minthara, Sazza/goblins, gnomes and tieflings. Wyll is still obligated to go looking for his father there + save Mizora and Karlach going all hero on the cultists/being on her way to Baldur's Gate to exact revenge on Gortash.