Lily watched the dog move toward James, worriedly checking him over to get a complete map of the things she would need to tend to, then gasped when the dog threw himself at James. It wasn't alarm so much as another flicker of that instinct that had said this dog was Padfoot, an instinct that was given real proof when he was a dog no more a few moments later, James falling back from his crouch onto the sidewalk with the impact.
For a moment, she stood there, shocked that this dog she had thought was Padfoot, then thought a stray, was Padfoot, but then that gave way to shock over his state. If she had thought Padfoot was too thin and in poor shape, it was nothing compared to the state of Sirius. It was impossible to deny he was almost skeletally thin, hair matted and knotted, his robes hanging on him as though on a coat rack, rather than a person.
But it was Sirius. She knew that as certain as she knew her own name. Closing the distance between herself and them, she dropped to the ground and wrapped her arms around both of them, burying her face somewhere in the vicinity of Sirius' back, making it impossible now for James or Sirius to get up, a comical bone pile on the sidewalk, if not for the heart pains of the situation.
"Oh, Siri, what's happened to you?" she whispered, crying without really paying attention to that fact.