Mojo weighs 4 lbs and I give him about a tablespoon when he needs it. I don't know that I'd start with 12 tablespoons as that seems like quite a lot even for a 50 lb dog but perhaps someone else can give you a better idea. If not, maybe try 5 or 6 and see how it goes? You can always give more if she needs it, but too much pumpkin can cause loose stools so I'd worry about giving too much.