Show her good side if we become close to her - the ability for friendship, love, self-sacrifice and all that.
You want to show her that after you murder a bunch of kids to get close to her? Lolol?
Yes, goblins - cannon fodder and minions, druids and tieflings - enemies of the Absolute who were ordered to destroy for some incomprehensible purpose. But the main character may well become important to her, and with the main character she will be completely different.
I think a much more needs to be done for this, and it will not necessarily be associated with evil.
Perhaps the Absolute will order us to kill Minthara in order to punish her for failure and take her place, and the main character will not do this, moreover, he will also protect her from the clerics of Lolth who also want to punish her for her betrayal. Add flowers and nice words to that. After that, she must understand something.
I would like Minthara to be available as a companion even if we are not helping the goblins, just under different circumstances, for example, if the main character takes her prisoner and then learns more about her background (to beat the redemption arc). If she joined the Absolute to avoid Lolth's cruelty, then perhaps she just didn't meet the drow Eilistraee? She is too interesting and charismatic character, and Larian needs to devote more time to her.
But in any case, this decision will be made by Larian - how exactly the Minthara content will look in the game, and what decisions can be made. I would like everything and a lot