I am so sorry to hear about Sadies experience. My little one had an experience with a black lab who was not tied and came charging out of his driveway when we were walking by on the sidewalk. Before I could grab her, he had grabbed her and shook her and flung her up in the air. I brought her to the vet's and she was bruised up but no bite marks thank god. Unfortunately it did traumatize her and she does not like big dogs at all and it takes her a while to warm up to small dogs as well. I know that it affected her as her first boyfriend was a rotweiller/doberman mix and he weighed 125lbs and they loved each other dearly. He went to the rainbow bridge before the black lab incident.
I would definitely take her to the vet for a check up just to be sure. If I had to do it all over again I would have exposed Bella to big dogs again right away but since Fred had passed over I did not have a big dog to trust to do that with so I did not pursue it. I wish I had. But ask the vet what he/she thinks.
I am glad to hear that Sadie is okay.
Good luck,
Jay