Party Girls is an online short story about Becky Allen and Raine Sengupta, which is published up on Alice Oseman's website. It changes between Becky and Raine's perspective and focuses on how they hook up, fall out, and fall in love over the course of a year.
The story takes place a year after Radio Silence takes place and two after Solitaire is taken place. during the course of the story it is shown that Raine Sengupta had a previous romantic relationship with Carys Last but Carys didnt think of it as such according to Raine. Becky Allen also brings up her old ex-best friend Tori Spring on numerous occasions.
Because this story wasn't officially published, it isn't necessarily canon, but can be viewed as such.