I actually read the 'Bree Taggert' series first by accident and loved it. Went back to 'Morgan Dane' later and it was fine—maybe even added some fun 'origin story' flavor to certain characters who pop up in Bree's world. So don't stress too much about a perfect order.
The connections are more about shared locations and occasional supporting characters showing up, not a continuous, chronological plot. Each book is a self-contained mystery. The timeline is really just the publication order of the books within their respective series. Starting with the first book of either major series gives you a solid entry point.
Look at the publication dates on the copyright page. Line them up from oldest to newest. That's your order. It's not rocket science. The author released them in that sequence for a reason—each book assumes you've read the ones before it, even if only in a general sense of the world. This isn't a franchise with a million retcons; it's a linear progression of an author's career. Respect the timeline she built.
Sometimes the publisher lists the order right on the book's copyright page or in the front matter. Check a physical copy or the 'Look Inside' on Amazon for the list of other books by the author. They often list them in series order. For Morgan Dane, it's clearly listed as a series with numbers or just in the sequence they were published. That's a foolproof way to get the order for that specific series. For cross-series chronology, you might need a fan-made list, but for a single series, the publisher's list is authoritative.
For ebook readers, check the series field in the metadata. It usually says 'Scarlet Falls #1', etc. That's the foolproof order. The connection is officially cataloged that way. Retailers like Amazon will also list them as a series in order on the author's page. So the technical, practical answer is just to trust the series number. The conceptual connection is the ongoing lives of the Barrett family in their town.
Her adult psychological thrillers are the main draw for most. I'd recommend starting with 'All the Missing Girls' because it put her on the map, then just follow your mood. Each book has a similar tense vibe but a unique setting.
I'm waiting for someone to mention the dog, Lady. Her role grows! In the first book, she's a new, traumatized rescue. By later books, she's a trusted partner and a symbol of the family's healing. That's a small but lovely arc that unfolds over the series. If you care about the pet companion aspect, read in order to see Lady's journey too.