I tend to get a little obsessive with tracking down authors, so I dug around before replying. I couldn't locate a well-known author named Jennie Wallden in major bibliographic databases, and there aren't obvious listings under that exact spelling in big catalogs. That doesn't mean she doesn't exist — it often means she's either self-published, uses a different pen name, worked on small-press or local projects, or has contributions in anthologies or magazines that aren't indexed widely.
If you want specifics, the routes I'd take are checking ISBN/issn databases, WorldCat, the British Library or Library of Congress catalogs, and retailer listings like Goodreads and the big online stores. Also search variant spellings like 'Jenny Walden', 'Jennie Walden', or 'Jennifer Walden' because name variations hide a lot of credits. Social media and author pages can reveal self-published titles hosted on platforms such as KDP or Smashwords. In my experience, indie authors can have perfectly legitimate backlists that only show up on niche sites or local publisher pages. Personally, I find the treasure hunt for obscure authors kind of fun — feels like following breadcrumbs — and I'm curious what you'd turn up next.