Rain's mother, who's implied to have died of cancer. This is because:
|contains major spoilers|
|After Rain's hair was cut, Fara asked her if she had any plans for the hair, suggested that it be donated. Rain asks if 'this is because of mom'. Thus, we can infer that the intended use of the donated hair was to create wigs for cancer patients who have lost their hair due to treatments (e.g. chemotherapy).|
In a flashback in chapter 19, she expressed homophobic views against Fara and 'Vivian', but Fara claims that "she was a lot nicer before she married that prick" (referring to Marcus Flaherty).