In Ellen Foster, why does Ellen's mother die?
Ellen's mother dies because she can no longer bear to live with her abusive husband. She commits suicide, taking an overdose of pills.
Ellen's mother is an unhappy woman. She comes from a wealthy family, and married Ellen's father against her family's wishes. Ellen's father turns out to be degenerate, drunk, and abusive, and Ellen's mother, a gentle, subservient character, labors under his insults. She has a bad heart, which is made worse by her husband's treatment of her. Ellen remembers her mother as being in and out of the hospital, and when she returns from her many stays there, Ellen's father "lets into her right away," demanding that she serve him with no regard for her own well-being. It is Ellen who tends to her mother, even though she is still very young.
Ellen's mother eventually reaches the point to where she can bear her husband's abuses no more. After returning from the hospital one last time, she swallows almost an entire bottle of heart medication. When Ellen and her father see what she has done, Ellen tries to seek help, but her father will not let her out of the house. Helpless, Ellen goes to her mother's bed and lies down next to her, cuddling with her until her mother's heart stops (Chapters 1 and 2).