When I get to the druids grove and talk to Arabellas parents, then go to Kagha to try and reason with her, Arabelle is not visible. Kagha and the snake seem to be looking at her though. When I talk to Kagha, she reacts like Arabella is already killed by the snake. When I talk to the druid Rath, he reacts like I saved her.
I have tried a new game, same result, and I sent in a bug report, but is anybody else experiencing this or is it just me?

other people have reported a bug like this yes, where the game gets mixed up about results but its normally a system error i.e, old game saves get mixed in with new games and that tends to be human error like loading old saves or using wacky antivirus

in any event Larian doesn't come here and their own forum is a bit of a joke as well so reporting bugs is best done on media like twiter... you still will not get an answer but at least they will see it