What to do about my Mom replacing 15 year old family dog?

Please give your mom the benefit of the doubt no matter how hard it must be for you. If I have a wonderful old dog who's end will be in a few years, I often will get a pup so the old dog can help teach the new dog how to be a good dog. Yes, I always train my dogs well, but some lessons are best taught/modeled by a dog who knows the ropes. An added benefit I have noticed is that it often picks up the old dog's spirits and makes them more energetic to have a young one around. I really feel the pups have helped my old ones live longer and better. Maybe your mom might be thinking this, too. Give Duffy an extra pet and hug from this old dog lover!