The court ordered for the 32-year-old to be cared for at secure psychiatric institution after a psychological evaluation found that she suffers from a serious psychiatric disorder.
The 32-year-old attacked the young woman in April at the Redbergsplatsen square, located in the city's Olskroken district.
Having pulled her victim to the ground by her hair, the 32-year-old straddled the other woman and inserted several fingers into her vagina.
The court considered that the woman's actions were tantamount to intercourse meaning that the crime could be classified as rape. The fact that the perpetrator was a woman was of no importance as the legislation on the matter is gender neutral, the court said.
Elisabet Kwarnmark, a psychologist and psychotherapist who has worked with sex criminals for three decades, said cases of this kind were practically unheard of. It was the first time she had ever come across the rape of a woman by another woman in Sweden.
"Female sex offenders are extremely rare. In the last ten years four women have been convicted of rape in Sweden. Any cases that come under investigation deal almost exclusively with children who are close [to the perpetrator] or rapes that also involve a man," Kwarnmark told newspaper Göteborgs-Posten.