Looking for a YA romance set at an elite private school (scholarship student, enemies to lovers)

I'm looking for a book I read maybe a few years ago (translated into Finnish, but I'm pretty sure the original is American).

Here's what I remember:

- It's the first book in a series.

- YA/New Adult contemporary romance with an enemies-to-lovers storyline and open-door/spicy scenes.

- The FMC gets into an elite private school on a scholarship because she couldn't otherwise afford it.

- Early in the book she catches a popular/rich girl secretly hooking up with a teacher.

- That girl's brother later blackmails his sister into keeping quiet about the affair, and he becomes the MMC/love interest.

- The FMC has a plus-size sister who designs and makes clothes for plus-size women.

- The MMC's family owns a clothing company/brand that originally made men's suits but now manufactures the school's uniforms.

- The FMC and MMC start out as enemies but eventually fall for each other.

I can't remember any character names, the title, or the cover. Does this sound familiar to anyone?