Shannon Richardson, 35, is charged with two counts of mailing a threatening communication and one count of making a threat against the president of the United States, the U.S. Attorney's Office for the Eastern District of Texas said in a news release.
Richardson, an actress from New Boston, Texas, was arrested June 7. She is accused of sending the threatening letters in May to Obama, Bloomberg and a third man who heads the mayor's gun-control group. Richardson faces up to five years in prison on each of the charges.
Richardson's court-appointed attorney, Tonda Curry, was not immediately available for comment Friday.
The government accused Richardson of mailing the letters and trying to pin the crime on Nathan Richardson, the man she married in 2011. He filed for divorce earlier this month. He's told the Texarkana Gazette that he contemplated divorce last year but reconsidered when the relationship seemed to improve.
The marriage was at least Shannon Richardson's third, and she has five children ranging in age from 4 to 19 from other relationships, according to Nathan Richardson's attorney, John Delk.
A federal judge last week ordered Shannon Richardson to undergo a psychological exam. Curry had requested the exam, saying her client had displayed "a pattern of behavior" that calls into question whether she could assist in her defense.
Authorities have determined that the ricin letters, which threatened violence against gun-control advocates, were mailed from New Boston, about 150 miles northeast of Dallas, or nearby Texarkana and postmarked in Shreveport, La.
According to an FBI affidavit, Richardson first contacted authorities to implicate her husband in the scheme. But she failed a polygraph exam and investigators found inconsistencies in her story, the document alleges.
Richardson later admitted she mailed the letters but maintained that her husband made her do it, according to the affidavit.
The actress has had minor roles on television and in films under the name Shannon Guess.
Copyright 2013 The Associated Press.