This happens when you see someone that you want to say so much more than "hey" to, but you can't for many unfortunate reasons. There's a bit of a pause or hesitation before simply saying "hey." You really want to declare that you are sweet on this person but it's not a good idea.
Juliette enters the room and she sees Romeo. Both look into one another's eyes. Juliette has feelings for Romeo, but he is with Desdemona. Juliette, feeling the mutterflies, gives Romeo a hesitation hey and then sips on her latte in shame.