Yeah, she was meant to be a generic background character at the school. Like below the importance of Jackie or even Oskar, and on the same tier as a crowd-filler like Chelsea or Hope or someone else whose name you wouldn't know if it weren't for anons desperate for content waifuing them in the early Season 1 days.
But someone happened to give her the "I want it to be my boyfriend!" line about Marco's sexy tentacle arm early in the first season, the crew found that funny and so Dominic continued on it by playing the "creepy" aspect of her up in Mewberty, and that stayed consistent in Interdimensional Field Trip too (I don't remember if there were any other episodes where she had a substantial amount of lines in that season, but off the top of my head I'll say no). Abby Elliot's voice performance apparently helped too, because it was like she was flirting with Marco while being an asshole.
So then when Season 2 rolled around they liked her so much they wanted her to appear more, so they made her one of Star's friends. Then in S3 she did mostly disappear like the Earth cast, only getting like 4 appearances outside of the opening and half of them just being brief cameos, and apparently it seems the crew liked her enough to find that a problem, because by S4 she actually was written into the overarching plot by appearing frequently on Mewni, due to having discovered the Earth portal to the Realm of Magic.
Pretty good for a planned background character.