I'm sorry your mom is threatening to break you and Misty apart. Perhaps you can do something to make the situation better though. Talk to mom and find out what it is specifically she doesn't like about Misty and then work to correct that behavior. You can perhaps strike a deal with her that whatever it is that bothers her will be corrected in 6 months time or so.

I'm not sure how old Misty is or if she has ever had any formal obedience training or not. Perhaps if you spent the time to take her to a formal class it would show your mom that you are serious about keeping her and will do anything for her.

My first dog was a Beagle/Dauchsund mix and my dad didn't like it either until I showed him that I was serious and took it to training classes. I was in 10th grade at the time and we still talk about it some 30 years later and talk about how that was the turning point for him. It was also the turning point for me becuase that is how I got started in dog training and I'm still doing it all these years later!

I hope this works out for you and Misty.