How is she a 'pet' character? I didn't notice her beating up any bad guys singlehandedly or anything like that - she played a peripheral role in the actual story, and vanished at the end of Englehart's run. Most 'pet' Mary Sue-type characters that I've encountered tend to be either the writer's attempt to create THE most villainous villain of them all, one who makes the rest of the hero's rogues gallery look (theoretically) like wimps, or a new supporting cast member who rapidly becomes the absolute center of the book, eclipsing almost everyone else. Because of this, these characters are left around at the end of the writer's run, with usually unfounded hopes that they will become classic characters that everyone will love, instead of annoying distractions. Now, while it's true that Silver is indeed still around, and did indeed become an important part of the Batman's life while she was there, she did NOT eclipse everyone else - Gordon, Robin, etc. were still around - she wasn't the center of the book, as mentioned before, and she rapidly removed herself from the scene at the end of the story, vowing never to return. That doesn't fit the qualifications for 'pet' character to me.