She wants rule the world, she told Astarion to do ritual and many other situation she act like evil character. Vengeance is her main goal but it doesnt mean she is good or even neutral.
So you should be happy that 2 others companions dont leave you after help thieflings. Becouse imo Laezel and Astarion should leave group too, like Wyll and Karlah if you help goblins. Playing as good character has only one consequence, you cant recruit Minthara. If you allow recruit Minthar like you want there will be no consequence for good character and it makes 0 sense too
