Those doubts came to a head July 7, when the 25-year-old Johnson fell to his death from a cliff in Glacier National Park while the couple was arguing.
Graham's murder trial began Monday. Federal prosecutors say the 22-year-old Kalispell, Mont., woman intentionally pushed Johnson.
Prosecutors presented jurors with dozens of text messages between Graham and her friend, Kimberly Martinez, that document Graham's emotional spiral from excitement about her wedding to despair about being married.
Federal public defender Kris McLean says Graham was having doubts, but Johnson's death was an accident and she lied about it because she was afraid nobody would believe her.
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