On that hot day in 2009, Bibi had a sip from the same container and some of the Muslim women became angry that a Christian had drunk from the same water.
They demanded she convert, she refused. Five days later, a mob accused her of blasphemy. She was convicted and sentenced to death. Later this month, the Supreme Court is expected to hear her appeal.
In January, the US State Department cited the law as one of the reasons as it put Pakistan on a watch list of countries accused of "severe violations of religious freedoms."
The move came as the Trump administration is ratcheting up pressure on Islamabad, freezing security aid until it cracks down on militant networks operating from its soil to carry out attacks in Afghanistan.
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Moreover, the Financial Action Task Force, an intergovernmental agency that combats money laundering and terror financing, has given Pakistan until June to show how it will tackle radicalism or else be put on a black list, a step that could hurt its international financial ties.
Often the law is used to punish rivals in personal feuds. Just making an accusation is enough to convince neighbors or others in the community that the defendant is guilty and must be punished, whipping up a vengeful anger even if the courts find the accused innocent. Authorities are often too afraid to push back against the public fury.
In at least one case, officials have kept a man acquitted of blasphemy in prison, fearing riots if he is freed.
"It has become much more dangerous over the last few years. The reason is that they have created a sense of fear," said Zahid Hussain, a political analyst and the author of two books on militancy in Pakistan. "It has become a ready tool not only against non-Muslims, but also against Muslims, who do not agree with their world view."
According to the US Commission on International Religious Freedom, 71 countries have blasphemy laws around a quarter of them are in the Middle East and North Africa and around a fifth are European countries, though enforcement and punishment varies.
At least 1,472 people were charged under Pakistan's blasphemy laws between 1987 and 2016, according to statistics collected by the Center for Social Justice, a Lahore-based advocacy group.
Of those, 730 were Muslims, 501 were Ahmedis a sect that is reviled by mainstream Muslims as heretics while 205 were Christians and 26 were Hindus.
The center said it didn't know the religion of the final 10 because they were killed by vigilantes before they could get their day in court.
While Pakistan's law carries the death penalty and offenders have been sentenced to death, so far no one has ever been executed.
Aasia's case even reached the Vatican, where Pope Francis last month met with her husband, Ashiq Masih, and daughter Eisham, who traveled to Rome to witness the Colosseum being bathed in red light in a sign of solidarity with persecuted Christians around the world.
During the emotional encounter, Eisham gave the pope a kiss that she said her mother asked her to deliver.
He spoke at a small Christian-run school in Lahore which Eisham and a younger, disabled daughter, attend. The school's principal and owner, Joseph Nadeem, has become a guardian to Masih and his children.
Masih, who said his wife was innocent, points to his arm where a bullet struck him, fired by a protester outraged with his wife's alleged crime. He never lives in one location too long, because it is potentially dangerous, he said.