The difficulty with Tinky-Winky isn't so much that she's aggressive, but more that she's unpredictable. I would say 95% of the time, if she meets another dog off leash, she will come back to me and nothing happens. Out of the other 5%, some times she attacks like a demon, especially small dogs... and some times, as in this case, I find her peacefully having a pee on a rock with a pug. Of all things, you'd think she'd hate pugs? Not at all. Maybe she just doesn't realize they're dogs at all.
In any case, that's my problem with her. If she was always aggressive, she'd never be off leash, and if she was never aggressive, she'd never be on leash... but you never know with her. That's the problem.