You're not going out with him/her, but you do like them, and they like you too. Basically you act like
you're in a
relationship and get jealous when they talk to the opposite gender.
(In Kelly's head): Danny is so cute!! Aww we would look so cute
together!!
Danny: Hey Kelly.
Kelly: OMGOMG ARHAERIHgshroihERK HI DANNY!
Danny: You cute. I'ma talk to Cindy.
Danny: Hey cindy,
you hot.
Kelly: WTFFFF WE'RE IN A CRUSHATIONSHIP!!
YOU BROKE MY HEART!
Danny: *just ignores* So yeah Cindy, Prom 201_?