Your fuzzy is quite an age now and she may indeed have doggy dementia, which would/could effect her bathroom habits, eating habits, and sleeping habits. Scolding her won't get the message across, as she may not even remember exactly what she did. The diaper is a good option and you may wish to go to that full time if she is found to have dementia/senility. The best advice would be to take her to the vet and ask the vet's opinion on her mental and physical condition. Sometimes dogs in old age will get odd bathroom habits when they have some sort of sickness or disorder, which is why a visit to the vet would be important. The other possibility is that your dog may be stressed out by some change made to the home or yard, new furniture, a new roommate or family member moving in, even moving things around could effect her state of mind and make her not want to use the outdoors for all her duties. But remember, just like elderly people, elderly dogs need patience, especially if they have dementia. And, just like old people, sometimes an old dog may have to go to diapers full time.