Glorfindel paused for a moment, to see if the troll was really down or not, since it wasn't, you know, down. He could still hear its heart beat, however, so it likely just got the wind knocked out of it. Even if she had managed to take it out in one blow, it never hurt to be sure, so he stepped in and shoved his sword up into the troll's mouth. Which was made simple by the position.