This whole 'no use of secondary sources/criticism' thing is absolutely bananas. Her dissertation will absolutely tank if she goes down this route, but hopefully her supervisor will manage to sway her decision. Even if you have an original project idea, you still need to engage with secondary material — countless academics will have worked on whatever she decides to do in some capacity, and even if she's proposing something entirely new, she'll have to engage with other resources in order to criticise their work, or 'prove it wrong' as I can imagine her putting it. I'm going into my final year too, so I don't have any firsthand experience of writing a diss, but my partner is just finishing up his PhD, which is quite specific in terms of literature, and the amount of reading and theory he has had to engage with in a project that absolutely has to be original is mind boggling. Similarly, I've written an essay that's about half of the length of a standard diss, and while I was engaging with primary sources such as manuscripts etc., criticism still played a massive role. At the very least, she needs to take a genetic approach to her project if she does go down the manuscript route, but I can imagine that would be a bit too much for her intellectually tbh.