I agree with Ghilly, when an older dog has troubles, whether it is trouble defecating or taking a walk, then the dog needs to be seen by a Vet. It isn't necessarily your dogs 'time' ... it could be something else bothering her, anything from allergies to an infection. My pug was 16 years old when she left this world ... even though she couldn't pee, poo or walk without help for years before she died, she was a very happy dog. I wouldn't give up on your dog as yet - she could live for many more years as yet. I hope so because they are such a joy! Take care and best of luck!!
If you feel something is not right with your dog, you need to take her to the vet to have her examined. It might just be that she is constipated and needs something to help her go. You won't know, however, until you have her checked out. This is not something that can be diagnosed on an online forum. She actually needs to be seen by a vet. Please let us know what the vet says.
Ghilly