If she had even the slightest amount of common sense and self-awareness, she'd avoid that option like the plague. She clearly knows how to game the system and construct an essay to get a high grade, and has a lot of experience doing that.
If she listens to her personal tutors and works with them to come up with a relevant dissertation topic instead of the barely-relevant Victorian nonsense she's been trying to shoehorn in, she'll be in a solid position to write something that'll score her a solid 2:1 at least.
Naturally, she'll be unhappy with anything that's not the highest first, but a dissertation is a much safer bet for her than writing fiction. Judging by Erimentha and the poetry samples she's shown, she would be absolutely crucified if she did a third year creative writing assignment. No way would she walk away with more than a 2:2 if she handed in 10,000 words of prose on a par with Erimentally Unstable.