If by “the biggest group in her religion” you are referring to the Catholic Church, that’s not true. While it certainly would be a mortal sin, really all of Protestantism is heretical, but the Chruch does not condemn any individual to hell. In fact, as St. John Paul the Great tells us “We know that hell exists because Jesus told us it does, but we don’t know for sure if anyone is there” If she was unrepentant prior to her death, she would likely spend some time in purgatory, but I suspect less time than I will spend in purgatory, as I should know better to avoid serious sin than she does based on her raisin’.