The 25-year-old is accused of murdering a 22-year-old woman in Askersund, central Sweden, in June. The victim was repeatedly stabbed before her body was then chopped up with a saw and knife.
"Both the accused and the victim had a relationship with the same man," prosecutor Lars Duberg told the TT news agency.
The murder was committed in an apartment where the 25-year-old is suspected of arriving with hammers, carving knife, sleep hormones, syringes and needles.
In police interviews she has stated that she did not intend to kill the woman. Her defence team have said the same thing and pointed out that she had made no plans for how to dispose of the body.
Swedish newspaper Expressen reported that the accused told the police that she went to her love rival's house to give her a fright but she panicked and the attack ensued.
She later returned to the apartment with three Ikea bags and is accused of chopping up the body and burying the remains. Body parts were belonging to the victim were later found in a forest.
The paper also reported that the woman allegedly went online to search for tips on how to carry out a murder in advance of the killing
"She denies responsibility for the murder," her lawyer Johan Eriksson told Expressen.
However, the prosecution believe there is plenty of evidence to secure a conviction.
"My opinion is that it was a deliberate killing," said prosecutor Lars Duberg.
The case has attracted sizeable media interest in Sweden as it involves a butcher-style killing involving two women.
On average there is just one dismembering type murder in Sweden a year. Usually the culprit is a man who has killed another man or a woman.
The trial is expected to last five days.