1. Michelle Tratchenberg and Ashlee Simpson
In June 2009, Ashlee Simpson and her hubby Pete Wentz were at a club and ran into his ex, Michelle Tratchenberg. Ashlee allegedly got drunk, and yelled mean stuff at Michelle, like "the whole time you were dating Pete, I was f---ing him!" while dancing "like a stripper." Low blow. Ashlee's publicist said it was a misunderstanding and Ashlee apologized later.