"It upset me when you went to dinner with Kathy over me."
"Okay. But she's my friend. We didn't have plans."
"I know. But I don't like her and it made me jealous."
That, my friends, makes you look like an ASS. So instead you just have to pretend you're not upset or offended and that everything's okay and let it eat you up from the inside. Which sucks.
Or you could, like, strive to overcome petty jealousy and grudges and to treat each person as an end unto themselves. But, like, really. Who the fuck are we kidding?