Abigail is innocent if we are to believe the Lady of the Lake.If you let her die, when doing the Noon wraith quest, you learn you can't do more for the wraith yourself because you have blood on your hands. You must seek the old withc or the lady of the lake to find a way to help. The lady says you can't because you've got an innocent's blood on your hands, and that person is Abigail.However, if you save Abigail, the old witch conveniently dies before you reach the village, while if you let Abigail burn, the witch is still alive. So, how does the old witch die when Abigail survives? The only thing you learn is from Abigail herself, who says the old hag died before she arrived, but we know she wouldn't die if Abigail did.So, unless we make the ridiculous assumption that this is all a game and for game design reasons the witch had to live, it seems to me that Abigail is innocent of the Beast but if you save her, she probably murders the old witch to take her place.