Yep, same guy. Though she hadn't exactly expected there to be two wizards here named 'Sirius Black'. But the dog thing explains a lot about Sirius' earlier comment about friends who aren't human.

"He turns into a dog?" she repeats, wrinkling her nose. "Wow, that's pretty rude."

Like, hello friend, I know you turn into a violent canid you can't control, I'm gonna turn into a dog at you. Neener.