Picked up a pony from a local pick up app and she was sporting this. Can’t tell if it’s just a children’s hair tie or from a toy line from the 80s-90s. I’m like 99% sure it’s not MLP at the least.
It does look very reminiscent of 80s/90s accessories, but nothing off the top of my head. You might try poking around Ghost of Doll and see if anything clicks.