It serves to further hammer home the idea that she'd much rather die in Baldur's Gate than ever return to Avernus.
It's almost like she has made up her mind and won't let you decide her fate for her. It's almost as if she doesn't accept that anyone would force her to live in literal Hell (again). It's almost as if people need to learn to respect her choice.
Larian has improved THE ending that we have in the game NOW. That doesn't mean they won't work on a new ending. All this doomposting is ridiculous. What did people really expect on such short notice? The game was released a month ago, we had two patches, one of them improved the ending by making her stance clearer.
Because there are so many options for trying to fix her engine, any new content would obviously take more time. Just wait. They have already said they have called in the voice actors again - for what do you think that is, if not for "tying loose ends" as they put it?