Why do girls get so jealous of other girls so easily?

my girlfriend sometimes gets upset at me when i hang out with other girls who happens to be my friends. somehow my girlfriend thinks a few of them are slutty and doesnt like me being with them at all. i told her they arent slutty and i have no interest in them anyways. idn i think she prefers me not to hang out with any girls at all but that aint possible because i cant abandon my friends like that