Mad at my mom

So my mom who is in her early 70s decided she wanted another dog. I tried talking her out of it because I didn't think she would be able to train it. Well about 7 months ago she ended up getting a puppy Brittany Spaniel. Sure enough as I expected the puppy is too much for her. She has mentioned since she got it that the dog won't listen and is ripping up her furniture. She gets frustrated so instead of working with the dog, it gets tied up to a leash in a room. I have told my mom on multiple occasions as well as my brother's that this is not ok and that is probably why the dog is acting the way it does. We have tried to work with tge dog ourselves to train it but we're not there constantly so it's not productive. I have tried to get my mom to take her to an obedience class but she wont. Well a few weeks ago my mom said she had enough and wanted to get rid of it. I feel so bad for this dog. I'm sure with a little bit of trying it would be a great dog. I would take it but I already have a dog and she doesn't get along with other dogs. My brother agreed to take it but he called me crying because he didn't really want another dog but felt like he had no choice. I'm so mad at my mom for putting the dog through all this and us feeling like we now have to take responsibility for a dog that shouldn't need to take responsibility for