You Again (2010)

"What doesn't kill you... is going to marry your brother."

Plot Summary

History -- make that high school -- may repeat itself when Marni learns that Joanna, the mean girl from her past, is set to be her sister-in-law. Before the wedding bells toll, Marni must show her brother that a tiger doesn't change its stripes. On Marni's side is her mother, while Joanna's backed by her wealthy aunt.