I used the example of Morrigan from Dragon Age earlier, but Morrigan's alignment never really changed. All that happened is that she revealed she's not as malicious as you initially think.
I think you are right, but there are some differences. Morrigan was never a servant of an evil God who dictated his will to her.
Minthara's personality it seems typical of the drow, she is proud, cruel, strives for power, but if you get to know her better, she had no choice, since she grew up in Menzoberranzan and was raised in such a society. And despite this, she really did not like Lolth's excessive cruelty, which goes beyond the usual rational selfish cruelty, in an attempt to get away from which she had the failure to choose the Absolute that makes her do the same. She is not happy with this, it seems as if she has no choice and just trying to have fun, which she does very badly (this is confirmed by some dialogues after trying to kill MC).
Her character will not change too much, but what alternative we can offer her depends on our decisions. It has the potential for various solutions. She can be quite happy with Eilistraee (although she will never be kind and modest, but she can stop receiving evil orders, stop suppressing sentimentality and affection for friends and loved ones), and with Loviavar or other Gods, and without God at all if in the person of the Main Character he gets a strong ally in order to be able to afford it