Jennie Garth sits down with “Extra’s” Derek Hough (her former “Dancing with the Stars” partner!) to dish on her new memoir, “I Choose Me.” She’s opening up about her life like never before — a painful divorce, multiple miscarriages, and behind-the-scenes drama and feuds with her “90210” co-stars. Jennie talks about her “blurry” relationship with co-star Luke Perry, as well as making peace with Shannen Doherty before her passing.