On snap!

A Jelena insider reveals:

"The first time Justin and Selena broke up, it was because Justin shot an episode of Punk'd with Miley Cyrus. Selena is repulsed by Miley! When Selena brought up her concerns to Justin about shooting with Miley, the pal says Justin shot her down. Justin did the show anyways, which didn't sit very well with Selena."