I love Jessie J's music, and this is one of my favorite songs by her. I think it sounds great on a violin, coupled with bathroom acoustics or something.
Also, decided to change the format to pdfs so hopefully music will print out correctly :D
Here is the free violin and mandolin duet sheet music for Cups, aka When I'm Gone, written by A.P. Carter and popularized by Anna Kendrick on Pitch Perfect. I created a harmony for it if you want to play it as a duet (the mandolin is irrelevant, it's just what I was using at the time). It's a short, fun little piece that is actually quite enjoyable once everyone stops overusing it.