If it had been an adult asking for his autograph, Obi-Wan would have walked away pretending not to understand. Or given the person a small lecture (as Obi-Wan was opt to do) on how such a miniscule possession was relatively meaningless in the great scheme of the universe and that diverting one's attention to matters of self betterment would be more productive. But the girl was just a youngling. And younglings needed people to look up to. Mentors. And children were often times much wiser than adults. She probably believed that he was more than just a storybook character. So he indulged her childish fascination.
Obi-Wan caught a momentary glance of the small interlude between the woman he thought he recognized and some fellow, but didn't hear their conversation. When she called out to him by name, Obi-Wan immediately lifted his attention and began walking towards her. Of course, he only took a few steps before he noticed the blood on her hands and instant concern set into his expression. He quickened his pace. And when he reached her his gaze was still intent on her injuries.
"You're hurt."
She knew him.
He raised his head to look at her face. She was familiar. She did look like the former Queen of Naboo. The resemblance wasn't uncanny, but it was very obvious that they could have shared a close heritage.
"What is this? Some kind of reinactment? You're supposed to be way older than that, dude!" The man who had bothered Leia said. Apparently he didn't have anything else to do with his time except criticize what he couldn't possibly understand. "You guys aren't real fans. Just posers. That's so lame."
Obi-Wan diverted his attention from Leia for a moment to wave an almost dismissive hand at the fanatic.
"You don't want to be bothering us. You're the poser."
The man blinked and his eyes glazed over.
"I don't want to be bothering you. I'm the poser," the man repeated, trance-like.
"You're going to go home and find something constructive to do with your time," Obi-Wan gently insisted.
"I'm going to go home and find something constructive to do with my time."
And the man walked away, allowing Obi-Wan to return his attention to Leia and her injuries.