Whatcom County Superior Court Judge Ira Uhrig ordered Misty Lee Dolan, who had previous convictions for theft and forgery, to serve 43 months in prison.
The Bellingham Herald reports her boyfriend, Manuel Valenzuela, who had far fewer prior convictions, was sentenced to six months.
According to court papers, a 78-year-old woman had her purse snatched as she was getting into her car outside of Target on April 22.
Police officers caught up with the couple in June. Valenzuela confessed, saying the crime was done on an impulse.
Both defendants pleaded guilty this week to theft in the first degree.