MEAN GIRLS TURN TO MURDER, ON "20/20," FRIDAY, NOVEMBER 19 ON ABC

And: Cynthia McFadden Interviews Cher About Her New Film, "Burlesque," Her Dating Life, Career and Motherhood

What started as a classic teenage rivalry � two girls locked in a tug of war over the same boy �quickly escalated into internet insults, and finally a deadly street side showdown. Growing up in the same Florida suburb, teenagers Sarah Ludeman and Rachel Wade had many things in common, including the same boyfriend, Joshua Camacho. The girls learned of each other through Myspace and then used the web as a place to taunt and bait each other with words and photos. As Joshua continued to date both of them, the animosity between Sarah and Rachel increased, creating a volatile mix of teenage passion and angst. It would all come to a head on a fateful night in April 2009, when words would turn into blows and lives would be forever changed. Ashleigh Banfield reports on "20/20," FRIDAY, NOVEMBER 19 (10:00-11:00 p.m., ET) on the ABC Television Network.

And: Cynthia McFadden sits down with megastar Cher for a rare, in-depth interview. The star discusses her new movie, "Burlesque," her co-star, Christina Aguilera, dating, whether there's a man in her life, and whether reports that she's worth more than $600 million dollars are true. She also gives her first extended interview about her son, Chaz. Formerly Chastity, Chaz underwent gender reassignment surgery.

"20/20" is anchored by Elizabeth Vargas and Chris Cuomo. David Sloan is executive producer.