Don't believe the "drew blood" part. However, in the video where she showed off the bite mark, you can see slight bruising (albeit very faint). So, i do believe he bit her.
One thing that's a bit jarring to me is how she turned on him on a dime. Years working together and after this incident, he's just a senior citizen to her now.
On the other hand, how stupid do you have to be to bite someone's arm like that? All he had to do is pretend to bite her arm if he was doing some sort of playful thing for the audience.