"We were capable of having children, but Astoria was frail. A blood malediction, a serious one. An ancestor was cursed... it showed up in her. You know how these things can resurface after generations..."
-- Draco Malfoy (CC4)
A Maledictus is a witch or wizard who suffers from a blood curse. One form of this affliction, referred to as a “malediction,” had been inherited by Draco Malfoy’s wife Astoria Greengrass. Astoria died from the blood curse in August of 2019 (CC).
Another form causes its victim to slowly transform permanently into a beast (CG). A Maledictus was the feature act of the Circus Arcanus. The highlight of the act was when a girl, Nagini, “melts into coils” transforming herself into a huge snake (CG43).
from "malady" = an illness or something that causes one to suffer. According to vocabulary.com: Malady, pronounced "MAL-uh-dee," comes from the Latin words male, meaning "bad or ill" and habitus for "have, hold." (Text from Vocabulary.com, Copyright ©1998-2017 Thinkmap, Inc. All rights reserved.)
Fan speculation a year before the film's release is that this woman's name is not given because she will be revealed to be Nagini. The release of the third trailer for the film on 25 September 2018 and a short interview with the Claudia Kim confirmed that she is in fact Nagini.