Hardison was so busy trying to make himself into a small ball of invisible, that he didn't hear Ava's squeak. Because even if he had, in spite of being invested in self-preservation, he would have called out how adorable she sounded. Thankfully for his lifeline, he didn't.
"So what, you're just going to send your demon buddies after me because I look so goddamn sexy? I don't care how cute you are, I CALL FOUL!" He shouted from where he was cowering. He really wish he knew more about demon fighting. Like how not to get killed in this particular situation. Sure, he knew some things from his time there and from the time he spent in the future, but how not to die? Yeah, well, he didn't know how he was going to do that here.
So he continued to talk, hoping to put her off by babbling at her until she grew tired of wanting to kill him. "I bet you couldn't kill me if you didn't have your demon friends! You think you're oh so powerful, but I bet you fight worse than I do one on one!"