Threw in for

"Please, Bella," she begged. "Give me some details.""Well... okay, I've got one. You should have seen the waitress flirting with him - it was over the top. But he didn't pay any attention to her at all." Let him make what he could of that."That's a good sign," she nodded. "Was she pretty?""Very - and probably nineteen or twenty.""Even better. He must like you.""I think so, but it's hard to tell. He's always so cryptic," I threw in for his benefit, sighing.

"I don't know how you're brave enough to be alone with him," she breathed.

What does "threw in for his benefit" mean?