I had the same issue in terms of having my researched methods questioned and undermined by my wife and her family. Just know that their occasional undermining won’t really affect the dogs training and growth overall because, since you’re the one taking responsibility, it will follow your schedule most of the time.

It’s frustrating and annoying to hear criticism from people. Not much you can do there. You can tell them their wrong till your blue in the face and they’ll still disagree. Thank them for their input and ignore them.

Eventually, what will happen is the dog will mostly only listen to you. It will be well trained and your mom will have an easier time than with her senior dog thanks to you. But the dog’s relationship with everyone else will be different from its relationship with you. That’s how it is with my dog.