I can see how that would be annoying. Have you discussed it with her? And if you discussed it, did you explain how it makes you feel when she does that?
I recently found myself snapping at my wife - finger snapping. Mostly it was because I was on a work call with the door shut and she was knocking to see if I was on a call, so I snapped my fingers a few times to try to let her know I was on a call. After I did it, I apologized to her, saying I wasn't trying to be rude, but I needed to let her know I was on a call and couldn't answer her at the door. She said she didn't think I was being rude, and she figured out pretty quickly why I was snapping.