How do I get rid of jealousy?

Im 16 and have bn going out with my girlfriend for near 5 months. I get jealousy surges sometimes. like for instance, last summer she liked a guy and was at a party and kids slept over during a co-ed sleepover. he never came but she said tht she wouldve at most slept on a couch next to him but not touching him or nething (SHE IS NOT A SLUTTY GIRL IN NEWAY, like she wudnt make out with random ppl, only do things with ppl shes going out). well tht boy never came tht night neway, and she wasnt "planning" to sleep next to him, but wouldnt mind. is this kinda provocative of her or am i being jealous, and if i am, how do i rid myself of it?