Usually when a normally behaved cat starts going outside the box, it is either due to a medical condition or a change in environment. I would suggest a trip to the vet to rule out anything medical first. Combined with the vocalization you are experiencing, I have to wonder if her thyroid is acting up. If it is, it is very treatable, and she is of the age where it is a definite possibility. If she gets a clean bill of health, consider any changes she has been through..they could cause this as well.
There are ways to help her with this if it is due to a change. First you can add a Feliway Diffuser to the room or hallway she messes in. This emits a calming to the cat pheromone scent that will help her with this behavior. There are also ways to deter her from her usual spot and get her back into the box. First, if you do not have 1 box per cat, you might try adding enough to get you there, and ideally, one extra. Some cats decide that they do not like to poop where they pee, nor do they like to share, so the rule of thumb is one box per cat plus one extra if you can, and be sure to scoop them daily. Add a product called Cat Attract to the boxes, as this has a very high success rate in getting them back in the box as well. If you have recently switched from an uncovered box to a covered one, remove the cover, she make not like it. (or vice versa). To clean the area she has messed and deter her from future messing, use a good enzymatic cleaner such as Nature's Miracle. That will remove all traces of her smell and keep her from going back to it. I wish you the best of luck with this, please let me know how she does!
Warm Wishes, Reani
Cat Care Expert
20+ years experience with Cat Care and behavior problems, 3 years Pet Rescue