@Alexandra, I know crossover isn't a genre. I was just pointing out that the author of the query she rejected because they called their work YA/Women's fiction was probably saying the work had potential in both markets. It's a crappy reason to reject a query.
Repeat Cyia's answer here.
In addition, in Query Letter Hell (QLH) we see a lot of virgin posters who want to argue that their novel has crossover potential. We try to squelch that immediately because it shows the individual doesn't understand how publishing works.
Starting point from publisher is the middlemen here, bookstores and libraries. Occasionally a book can get two shelf spaces in bookstores and libraries, but those are the exceptions to the rule and are the long shots. Agents and editors do not play to long shots. So if a book is only going to get one shelf space in libraries and bookstores, it is going to be either YA or adult. I've yet to see a library or a bookstore that has a section called crossover.
So how does a publisher deal with this division? Very simple. Editors, by and large, are either adult editors or YA editors, and publishers that are large enough have an adult department and a YA department. Although editors can see when a book might appeal to both adults and YA, they understand they have to work within that division.
Crossover is a readership issue, not a publishing issue. Although everyone is aware of it in the industry, arguing that your book has crossover appeal shows a lack of understanding of the industry. Almost as bad as referring to your book as a fiction novel.
And from the point of view of an agent (which I'm not), would I want to spend time with a writer teaching them about publishing, material which is widely available? Because quite honestly, a writer is going to have a lot to learn about publishing even with a significant level of knowledge about the industry.
She's not the only agent who uses things like this to gauge a writer's knowledge of publishing. And to reject writers who haven't done their homework. I don't blame her.
Best of luck,
Jim Clark-Dawe