Yeah ... sadly as far as im concerned, i am not down for the avernus ending, or for them to change karlachs dialogue/ story for that ending* to make sense* . Her endings currently are failed states, plain and simple. The avernus eoilogue attempts to put a positive spin on that failed state. I also HATE being railroaded in a game like bg3. Espically as she is the only companion to suppossedly be railroaded.
Ive said once ive said it again and ill say it one more time In a game of 17k supposed endings, you should not be forcing* a tragedy on the player with a companion character. There should be a way to save her and let her stay. To allow players the CHOICE. As with every other companion you get.