Campaigners condemned the ruling, saying it violated international standards and raised concerns that Sudan might start applying sharia, or Islamic law, more strictly following the secession of mostly non-Muslim South Sudan last year.
The woman, Intisar Sharif Abdalla, was sentenced by the Ombada criminal court on April 22, court documents seen by Reuters showed.
Two lawyers assigned to her case, who declined to be named, said they were launching an appeal adding Abdalla appeared to be under severe psychological strain.
"She's in dire need of a psychiatrist because she appears to be in a state of shock from the social and family pressures she's under," one lawyer said.
Abdalla was illiterate and did not have a lawyer or interpreter in the courtroom, although Arabic is not her native language, the lawyers and activists added.