In "Rappaccini's Daughter" by Nathaniel Hawthorne, Beatrice dies when her lover Giovanni gives her a potion that destroys the immune system that had protected her against the poisonous flowers in her garden. As Giovanni states,

It is composed of ingredients the most opposite to those by which thy awful father has brought this calamity upon thee and me. It is distilled of blessed herbs.

It is accidental death. Giovanni had hoped by giving her the potion they would be able to leave the garden and become proper lovers. The only time she had touched him before he had felt a "burning and tingling agony in his hand" When he turned his hand over he saw that it had turned purple.

Unfortunately, she takes the antidote while she is still in the garden. She had been protected so long from the poisonous plants that her body can't take it, and she dies at the feet of her father and Giovanni. At the end of the story the man who gave Giovanni the antidote, Baglioni, leans out of a window and says, "in a tone of triumph mixed with horror," “Rappaccini! Rappaccini! And is this the upshot of your experiment?”

Beatrice is poisoned -- sort of. Her father, a "mad scientist", conducts experiments on plants and flowers, trying to grow the most exotic and beautiful ones he can. His botany experiments are poisonous, however. Rappaccini also experiments on his daughter, Beatrice, giving her poisons as well, but to improve her, to make it so she can kill someone just by breathing on them, among other things. Rappaccini gives the same poisons to Giovanni, Beatrice's boyfriend, in an attempt to make him become like her and not succumb to the poison. When Giovanni tells Beatrice what her father has done, she swallows the antidote, but because she is so infused with the poisons, the antidote winds up killing her.

Read about it here on eNotes.