Kisa Gotami has two of the most heart-rending stories in the Buddhist tradition associated with her name. The Commentary to this verse tells that when her young child had died, she refused to believe it was dead. After asking many people — in vain — for medicine that would revive the child, she was finally directed to the Buddha. When she told him her story, he offered to provide medicine for the child, but he would need some mustard seed — the cheapest Indian spice — obtained from a family in which no one had died. She went from house to house asking for mustard seed, and no one refused to give it to her. But when she asked if anyone had died in the family, the universal response was always, "Oh, yes, of course." After a while, the message sunk in: Death is universal. On abandoning the child's body to a charnel ground, she returned to the Buddha and asked to be ordained as a nun, and afterwards became an arahant.
The canonical verses associated with Kisa Gotami's name, however, tell a different story, which is identical to the story that the Commentary attributes to Patacara: Pregnant with her second child, she was returning to her parents' home, along with her husband and small firstborn child, to give birth. Along the way, a great storm blew up, and she asked her husband to provide shelter for the family. As he was cutting grass and sticks to build a shelter, a snake bit him and he died of the poison. Unsheltered, and wondering at her husband's long absence, Patacara gave birth and had to spend the night sheltering both her children against the rain and wind with nothing more than her body. The next morning, she found her husband dead. Distraught, she decided to return to her parents' home. However, a river — swollen from the rain of the previous night — ran across her way. Unable to carry both children across the river, she left her first-born on the near bank and waded through the raging current carrying her baby. Placing the baby on the far bank, she turned back to fetch her first-born. A hawk, seeing the baby, took it for a piece of flesh, and swooped down on it. Seeing this, Patacara raised her hands and tried to chase it away, but to no avail: The hawk picked up the baby and carried it off. Meanwhile, her first-born — seeing his mother raising her hands — took it for a signal to cross the river. As he jumped into the raging current, he was carried off to his death. Overwhelmed with grief, Patacara returned to her parents' home, only to learn that it had burned down from a lightning strike in the previous night's storm. Her parents and brother were at that moment being cremated on a single pyre. At this point, she went mad and began wandering around half-naked. Only on coming into the Buddha's presence did she recover her senses. He taught her the Dhamma, and eventually she ordained and became an arahant.
Why this story is attributed to Patacara in the Commentary when it is obviously Kisa Gotami's in the Canon, is hard to tell. Some scholars have suggested that the tales in the Pali commentaries were imported from other Buddhist traditions, such as the Mulasarvastivadin. Thus, the differences between the canonical verses and the commentarial tales stem from the fact that the different traditions attributed particular stories to different elder monks and nuns. For instance, the Pali Canon attributed the story of the woman whose family was destroyed in a single day to Kisa Gotami, while the tradition from which the Commentary drew attributed it to Patacara. If that's the case, it's interesting to note how the commentators who adopted these tales nevertheless remained faithful to their Canon. Instead of trying to change the Pali to fit with the commentarial source on which they drew, they allowed the discrepancies between the two sources to stand: one of many instances in which the discrepancies between the Canon and the commentaries suggest that the monks who handed down the Pali Canon tried to keep it intact even when they didn't agree with it.
Later Theravadin texts have tried to cover over the discrepancies between Kisa Gotami's verses and the Commentary to those verses by insisting that the passage in the verses beginning, "Going along, about to give birth," and ending, "my husband dead, I reached the Deathless," is actually Patacara speaking, but this seems unlikely: Why would one arahant butt in on another one's tale?
At any rate, regardless of which story is Patacara's, and which Kisa Gotami's, both speak to the universality of death, and the power of the path of practice: that in the midst of this human world with all its sorrows, there is still a way to find that which is free from grieving, aging, and illness: the Deathless.
See also: ThigA X.1, the Commentary to this passage.