The 41-year-old woman's father was found dead at a cottage outside of Arboga in Central Sweden in August this year.
She was later arrested along with her 18-year-old boyfriend in Norway on suspicion of murder.
Earlier last month, at a graveyard in Gustavsberg near Stockholm, the police brought up the remains of the woman's late husband, who was found in Lake Hjälmaren near Arboga in August last year.
His death was treated as an accident, and no suspicious circumstances were found during a post-mortem examination. However, after the woman was arrested on suspicion of murdering her father and the attempted murder of her mother, the prosecution office decided to take another look at the husband's death.
On Thursday, in a statement, prosecutor Johan Fahlander said that there is reasonable suspicion that the woman killed her husband, and that she denies the crime.