"I honor her memory by voting for this bill," Davidson told her colleagues Wednesday after the controversial measure was approved. "So women will no longer walk into a licensed health-care facility and be butchered as she was."
By Thursday night, Gov. Corbett was saying he would sign the bill, and Davidson was being hailed as a heroine by the antiabortion movement.
The clinic bill grew out of the uproar over physician Gosnell's now-shuttered clinic. Indicted by a Philadelphia grand jury last January, Gosnell is facing eight murder charges in the deaths of seven babies and an adult patient - not Shaw - in a filthy clinic that investigators described as a house of horrors.
Shaw's death, which led to a $900,000 insurance settlement, was central to the grand jury's conclusion that state officials had failed to inspect the clinic for two decades and repeatedly ignored complaints of possible criminal activity there.
Davidson, 49, who grew up in same Mantua neighborhood where Shaw lived and the Gosnell clinic was located, said her young cousin probably sought an abortion because she had two young children and realized that as a single woman, she could not support a third. The grand jury report said Shaw had four previous abortions.
Little wonder the clinic wasn't inspected in those days, Davidson reasoned. "The regulations regarding inspection were only policy," the legislator said. "It was not mandated by the law."
The grand jury report's horrific account of babies delivered alive and killed with scissors, and mutilation of patients - all at a clinic not visited by state health inspectors for years - cracked open the long-dormant abortion debate in Pennsylvania. Corbett ordered firings in the state health department, and legislators crafted a bill that would place the clinics under many of the same regulations that govern hospitals.
Opponents of the bill included the Hospital of the University of Pennsylvania and other hospitals, as well as the American College of Obstetricians and Gynecologists. Abortion-rights advocates predicted that many if not all 22 freestanding abortion clinics in the state would close because they could not afford to comply with the bill's hospital-level construction and staffing standards, and called the bill a Trojan horse for abortion foes.
Davidson does not share those concerns.
"I don't often buy into conspiracy theories. There is no evidence to support that that would happen in Pennsylvania," she said after the vote. "There is a long list of organizations [that oppose the bill] that have resources to raise funds to make sure clinics stay open."
Elected in 2010, Davidson is the first African American, first woman, and first Democrat to represent the 164th District.
Davidson's stance on the clinic bill drew a wave of praise from abortion opponents. The Pennsylvania Family Institute, praising the state House's 151-44 vote on the bill, said the group "salutes the courage of Rep. Margo Davidson" for her vote.
Davidson described herself in an interview as having "pro-life leanings," but said she did not want to overturn Roe v. Wade. "I don't want to go back to back-alley abortions that put a woman's life in danger," she said.
But she said she felt compelled to support the bill because her cousin's case exposed fatal flaws in the system - complaints ignored, leading to tragedies that could have been prevented - and because she cannot forget the cries of her young relatives as they stared at Semika's body at her viewing.
"They were screaming and demanding she get up," Davidson said. "There was no way I could comfort them."
In one way, her vote on the abortion bill was not a first for her. It is the second time in her brief tenure in Harrisburg that she has connected her legislative stance to a family tragedy.
In April, Davidson stunned fellow lawmakers with a tirade against State Rep. Daryl Metcalfe (R., Butler) during a floor debate on the so-called castle doctrine bill, which expanded the rights of gun owners to use their weapons in self-defense.
"If the gentleman from Butler County stood yelling," Davidson asked, "knowing that he's a gun-toter, and I felt threatened, would I be protected under court law if I blew his brains out?"
She said those comments were driven by the slaying of her only brother, gunned down in Philadelphia several years ago during a home-invasion robbery.
"I've experienced firsthand basically any tragedy available," Davidson said Thursday. "I've had to come through a tremendous amount of hardship to be who I am."
Contact staff writer Amy Worden at 717-783-2584 or firstname.lastname@example.org, or follow on Twitter @inkyamy.