The maid

Milly was nothing but a boarding school student before she was accidentally turned into a killer with a ten-year criminal record after saving a friend from a rape incident; after her release from prison, she lived in her car and searched for work, a job that would provide her a place to live, and she had a share in the wealthy Winchester family's house, so this job was her last chance for a new beginning. She hides her secret behind her, before discovering that the secrets of the Winchesters are more dangerous than her secret. Milly begins her new job after Nina Winchester contacts her and asks her to work as a maid; Milly agrees to the job for an attractive salary she did not expect. The days pass normally at first, she brings the daughter from school, prepares a delicious meal for the family members, even imagining herself living Nina's luxurious life with Andrew, before she finds out what is being planned for her! Nina thought she was living a stable life with Andrew, who seemed perfect to the point of disbelief, but after months she found herself a hostage to a sadistic and evil man who enjoyed torturing her; imprisonment in the attic is his preferred punishment, and leaving it can only happen under conditions she must fulfill. Nina didn't understand what was happening at first, and with the repeated incidents of imprisonment, she started looking for a solution to free herself from her situation, which she found in hiring a maid in the hope that she would become her replacement, assuming that if Andrew fell in love with another woman, he would allow her to leave. But hiring Milly, giving her a copy of the attic key, and convincing her that it was her bedroom, and leaving a pepper spray bottle in the blue bucket in the closet, was only a plan to kill her. However, Milly did not know that. Someone ended up dead in the attic due to dehydration. Who/what was it, and what happened in the Winchester house after the maid was appointed?