In a sentencing memo filed in U.S. District Court, prosecutors said 61-year-old Catherine Greig hid Bulger's identity and handled the daily tasks necessary for them to keep a low-profile in Santa Monica, where they were captured last June living in an apartment.
Bulger, 82, was the leader of the notorious Winter Hill Gang. He was charged with participating in 19 murders and is awaiting trial.
Greig pleaded guilty to three charges in March and was scheduled to be sentenced Tuesday. She admitted using multiple aliases and obtaining Bulger's prescription medications by pretending to be his wife.
Although the charges carry a maximum of 15 years in prison, federal prosecutors had warned family members of the people Bulger is accused of murdering that she could get as little as 32 months under federal sentencing guidelines.
In their memo, prosecutors said Greig deserved a much longer prison term.
The Associated Press contributed to this story