Well she does leave the game Toggle Spoilerafter you get the note if you refuse her in the cellar... Unless you get the note that way I did several times.. I ate the blue mushroom while at the house and after the "Unsealing" of the grave. when I got to the cellar the door is working some times. Even without using the light 3 times on the horse dung if you want me...
No big deal. Its not at all important I just thought of it because the quests are close together on the game map and in the story line. And it would be satisfying for some.