Rebecca Serle 
When You Were Mine [EPUB ebook] 

Rosaline has been best friends with Rob since they were little kids. Recently, something deeper and more electric has entered their friendship, and when Rob returns after the summer break and asks Rosaline on a sort-of date, it seems they are destined to become a couple, just as Rosaline always knew they would be. The next day at school, a mysterious, beautiful girl arrives: Rosaline’s long-lost cousin, Juliet. And suddenly it looks as if Rosaline might be about to lose her best friend AND her new boyfriend