Who is she?
Ellen Berent is a young woman who becomes enraptured by an author named Richard Harland who resembled her birth father whom it is implied that she forced into a one-sided incestuous relationship to the extent that he died because of it. She breaks off her intended marriage with a lawyer and marries Richard. When Richard's younger paraplegic brother arrives to their home to stay, she becomes jealous and indirectly kills him by allowing him to get tired and drown in a river. Later, she wanted Richard to notice her again so she allows herself to become pregnant. But then she rationalizes that her unborn son could potentially take her husband's attention, so she tosses herself down the stairs and has a miscarriage.
When Richard found out what she had done, she forges a note accusing her half-sister of murder and poisons herself. Her sister nearly gets found guilty for murder, but Richard confesses to what his late wife had done and he is sentenced to a few years in prison for withholding that information.
Why She Doesn't Qualify
For one, she has a low body count with her indirectly murdering Richard's brother by letting him drown. I had initially thought of her as qualifying under the category because of the shock of having a character deliberately insight a miscarriage in herself. But...heinous wise, she doesn't breach the general heinous standard. She is bad in the film as she is the only villain in it, but overall, she does not meet the absolute part of the criteria. She crossed the moral event horizon for sure, but she otherwise fails the absolute heinous standard.