Frodo blushed and pulled his hand away. "Oh, um..." And then he didn't know what to say, so he just smiled instead.
He turned to Coulson once she was gone, lowering his voice a bit. "I doubt you would have said anything, but just so you know, I am aware of the fact that she's several years younger than I. It's not typical of me. I don't want you to get the wrong idea."
Coulson had, after all, seen Frodo's home and had some idea of his income bracket.