Is my mother, who drowned in a well about twenty years ago and was a righteous woman, considered among the martyrs?

The drowned person is a martyr, according to the Prophet, peace and blessings be upon him, who said: "The martyrs are five: the one who dies of plague, the one who dies of a stomach ailment, the one who drowns, the one who dies under a collapsing building, and the one martyred in the way of Allah."