Ann Marie Hanrahan was busy, first as a partner at a Minneapolis law firm, then as a vice president at 3M. But the attorney always made time for her youngest clients: foster children whose cases she took pro bono.

Hanrahan gave them her brilliant legal mind — and her cellphone number.

“With a million and one things to do, she always managed to be available when I needed her,” said Nina Boswell, who was in high school when she met Hanrahan via the Children’s Law Center of Minnesota. “I would call her at midnight, and she would answer the phone.”

Whenever she had a spare hour, said her husband, David Prince, “she would devote it to pro bono work.”

A litigator, arts lover and advocate for children’s legal rights, Hanrahan died March 23 after a battle with breast cancer that spread to her brain. The Lake Elmo resident was 58.

“One of the things we shared in common was a quite intense feeling that, as a lawyer, you have a privileged position in our social order,” said Prince, also an attorney. “That brings with it a responsibility to try to make the community a better place, to help people who might be treated unfairly.”

Born in Green Bay, Wis., Hanrahan grew up in Florida playing violin and viola, drawing and illustrating and dancing ballet — talents that would lead to a lifelong love for the arts. After she graduated from the University of Florida, she returned to the Midwest, graduating from the University of Wisconsin Law School in 1988.

At Faegre and Benson, Hanrahan represented businesses and corporations and made partner as a young, single mother. She and Prince, who had two sons of his own, married in 1998. The couple traveled, exploring food and opera in Italy and elsewhere, partly as a way to carve out time together.

In 2001, she moved to 3M, where she became vice president and associate general counsel for litigation and preventive law.

Leaders there appreciated her ability to whittle down the number of claims against the Maplewood-based company — from 90,000 in one case to 2,500, said Janell Pepper, assistant general counsel. “She designed and implemented a strategy that helped reveal the medical fraud that was underlying the overwhelming majority of these cases,” she said, ridding the process of litigants who were “diverting resources away from people who were really ill.”

As a manager, Hanrahan was quick to praise and promote others’ work, Pepper said.

“She never bragged about herself, and I can tell you, she had a lot going for her that was worth bragging about,” she said. “But that was not her personality.”

So not many knew about Hanrahan’s recent role on the board of directors for the Guthrie Theater. Or her years of work with the Children’s Law Center, a St. Paul nonprofit that trains volunteer attorneys to represent children, including children who are removed from their homes because they’re in need of protection.

Boswell was 15 years old, fresh off a fight and set to be expelled from Coon Rapids High School when she — a little sarcastically — asked for a lawyer. Hanrahan took her case. At first, Boswell was “a bit snarky and standoffish,” she said, convinced that Hanrahan, like other adults in her life, would end up leaving her.

But Hanrahan never did. She brought Boswell’s case twice to the Minnesota Court of Appeals, winning a decision that protects students from being expelled without sufficient notice and explanation, said Lilia Panteleeva, executive director of the Children’s Law Center. “You talk about changing lives … this is now precedent in Minnesota.”

Even afterward, Hanrahan kept in close touch with Boswell, who is now 25, taking her out for lunch, helping out her siblings, attending her birthday celebrations.

“She was the most influential individual in my life,” said Boswell, who is now on the law center’s board. “She continuously planted new ideas in my head and things to inspire or reinspire my future, as if I were a blooming flower.”

Survivors include her parents, Robert and Mary Ellen Hanrahan; siblings Sheila, Robert Jr. and Pegeen; son Matthew; stepchildren Michael and Peter Prince, and two granddaughters. Services have been held.