The defendant is accused of setting fire to the house in south-central Finland, leading to the death of two of her relatives, a woman and her adult son.
The prosecutor in the case confirmed to the STT news agency on Thursday that two charges of murder are being brought against the accused.
According to a report in the newspaper Ilta-Sanomat, the accused was related to the two victims. The female victim was confined to a wheelchair and her son, who also perished in the blaze, was intellectually disabled.
The father of the family was not home at the time of the fire.
The prosecutor declined to comment on a possible motive. The case will come before the Pirkanmaa District Court at the end of this month.