I currently have a flex tri-fold hard cover. It's nice that it fits flush. I have also had an extang that sat on top of the bed. I actually liked the extang better because it was quicker to take off but what I really liked about it was that I could walk on it.
Most any truck made in the past 25 years has a locking tailgate. But if it doesnt, there are a few options, most trucks you can get a locking latch for, it either replaces the factory latch, a flip kit that places the latch in the bed and has a filler panel that fits where the latch was, a locking cover for the factory latch, or the one piece fiberglass covers that actually fit over the bed rails and tailgate, they lock and the edge of the cover prevents the gate from opening.
I have a Leer Fiberglass hard Tonneau on my Ram 2500. IT works well makes the truck look fantastic but in the end i wish I would have gone with the Full Leer/Snugtop shell. Cab High model. THey do look great and have more utility than the Tonneau I have. What is your wife wanting in a cover? What use in particular?
I put a Roll n Lock on my Tacoma. I like it pretty well. Leaks a little water but not very much. Dust is more of a problem. It's great for traveling with luggage and fishing stuff. Locks to the tail gate. Prevents opening the tail gate which I like. Its held up really well for some years. Cost plenty though. All the solutions involve some kind of compromise.