“This is a woman born in 1973. She was apprehended at 6pm on Wednesday and was formally arrested at 8.45pm," said police spokesperson Eva-Lotta Hermansson Truedsson to news agency TT.
According to prosecutor Magnus Larsson, the arrested woman could be described as close to the victim.
He said that the woman is under suspicion of instigating the murder and that it is possible that the circle of suspects could widen.
The 19-year-old woman was found dead just before midnight on Monday in her apartment in Landskrona in southern Sweden, with multiple stab wounds to her body.
Currently, it doesn't seem as if either of the two apprehended suspects will be released.
“Not the way it looks right now, but there are a number of measures being carried out and the situation could easily change,” said the prosecutor to TT.
Police arrested the woman's 16-year-old brother after finding him outside the apartment, the Aftonbladet newspaper reported on Wednesday.
It has been alleged that the boy killed his sister for disgracing their family by having several boyfriends and trying to build a life for herself away from home, but this has not been confirmed by police.
On Wednesday it became known that the 19-year-old had been feeling threatened for some time and had been in contact with a support group, which was trying to fix her up with sheltered accommodation in another municipality, through the National Board of Health and Welfare (Socialstyrelsen).
The national organization Glöm aldrig Pela och Fadime (GAPF), a group honouring two of Sweden's most publicized cases of so-called “honour killings” has now reported the municipality handled the threats that the 19-year-old girl was living under.
The group is questioning whether the authorities have been observant enough of the increased threats against the woman before her death.
The municipality also asked the county administrative board (Länsstyrelsen) to review their support measures for women who live under threat.