I wonder if maybe this lady just rescued this dog and is still learning about its behavior. It's very unfortunate that she allowed three dogs to be terrorized, but it sounds like she did the right thing taking the dog out of the park.
I know here in SF I wouldn't say anything to the city because the mayor is trying to restrict dogs' access to a whole bunch of areas.
It's ridiculous, considering how many dogs there are in the city and how most of us don't have yards. I don't know about Seattle, though.