That said, the Prius is designed to beep continuously inside the cabin when put in reverse. The idea is that, because the car is so quiet, some drivers might not realize that the car is in reverse when they are trying to put it in drive or think it is in park (although I would think this could be a problem with any car). The beep is similar to the sound made when large trucks back up; however, unlike them, it cannot be heard outside of the car.
The problem was enough of an irritant that I looked for solutions online. Until 2010, this was a problem that Prius could fix on their own using a complex set of button-presses (which sounded a great deal like casting a magic spell) in set intervals. Doing so could turn the beep to a single beep that goes off when the car is first put into reverse, or could turn the beep off entirely. Unfortunately, beginning with the 2010 model (Mera is a 2014), the only way to fix the issue was to interface with the car's computer directly. For me, that meant taking it to the dealer. Online discussions on this topic said that Toyota dealerships should be able to take care of the problem at no charge.
I had to pick up my new plates at the dealership anyway, so I figured that I would have this checked too. It took a bit of haggling (the first two people didn't know it could even be done and then they wanted to charge a little over $50 for a 1/2 hour of labor), but the person in charge of the service area was willing to switch the beep for free.
Now, Mera only gives a single beep to remind me that I have set her to reverse. It is a much better arrangement. While I don't doubt that Mera and I will have future disagreements, I am glad that this one was able to be resolved with almost no trouble.