U.S. District Judge Donald Molloy said he saw no remorse from Jordan Graham, 22, in the killing of 25-year-old Cody Johnson. He also ordered her to pay $17,000 in restitution.
Prosecutors said Graham lured Johnson to a steep cliff in Glacier Park on July 7 and pushed him over, then lied repeatedly to investigators in an attempt to cover up the crime.
She pleaded guilty to second-degree murder just before closing arguments during her December trial, but tried unsuccessfully to retract that plea after prosecutors recommended a prison term of 50 years to life.
Prosecutors dropped a first-degree murder charge and a count of making a false statement to authorities when Graham changed her plea.
Before he accepted her plea in December, the judge asked Graham to tell him what happened.
Graham said she decided to confront her husband about her marriage doubts, but she did not know how he would take it. She said the couple climbed down a treacherous slope below a popular spot in the park called The Loop and spoke on a narrow ledge, hundreds of feet above a ravine.
She told Johnson she was unhappy. They argued, and at one point, she said, he grabbed her by the arm, and she thought he was going to pull her.
She told the judge she got angry at Johnson, brushed his hand away, then pushed him, with one hand on his arm and one on his back.
"I wasn't thinking about where we were. ... I just pushed," Graham said.
She said she then drove back to her home in Kalispell.
Johnson was reported missing July 8 when he failed to show up for work.
Graham initially told investigators that Johnson left their house July 7 with unknown friends. But Johnson's friends testified they were suspicious of the story and suspected Graham played a role in his disappearance.
Graham showed police a fabricated email - purportedly from a friend of Johnson - that said Johnson was dead and to call off the search.
She later told Glacier rangers she had found Johnson's body near The Loop because it was a place he wanted to see before he died. Ultimately, Graham acknowledged she was with Johnson on the cliff after investigators confronted her with a security camera photo of the couple entering the park.
Prosecutors presented jurors dozens of text messages between Graham and a friend from church, Kimberly Martinez, that documented how Graham's nervous excitement at the prospect of the wedding turned into despair over the week that followed.
Graham's attorneys tried to chip away at the prosecution's depiction of her as a cold, dispassionate woman who didn't want to marry Johnson, as well as their contention that she deliberately pushed him to his death. They also showed jurors videos of the couple's June 29 wedding and their first dance.