Those first five words are her problem in a nutshell.
1. You can have just the first three chapters done if you can't afford the full book. We are talking £ hundreds not £ thousands.
2. The blogs are free. Would seriously recommend her going to look at John Barnes's Book Doctor Blog and trying the various tests and tools - there might be some nasty surprises in store for her regarding her book. It is one of the major skills for a writer to be able to stand back and see their own work clearly. Sometimes just reading and re-reading it doesn't work. One of the items in the blog is how to examine dialogue, another is on action scenes and a third is on what each scene achieves. (Which is pretty complicated). He makes the point that there are a lot of books out there which aren't quite good enough due to technical writing errors (which is what Book Doctors fix) and once those are fixed, with essentially the same stories and characters, you then have a saleable book. Whether it will then actually sell is another matter that depends on taste, fashions in the market and what vision and editor has for their list but she will then be a lot closer.