Mary R. Thompson, 58, of Bryn Mawr and Sea Isle City, N.J., a medical practice administrator for three decades, including the last 12 years at Children’s Hospital of Philadelphia, died Sunday, Nov. 3, of a stroke at Bryn Mawr Hospital.

There were no signs that anything was wrong until she became ill on Oct. 29. “This came out of the blue,” said her husband, Michael J. Thompson.

Known as ‘Missey,’ Mrs. Thompson was full of energy and packed her days with activity, said close friend Lisa Dunhour. The two took spinning classes early in the morning, went on trips, swapped the books they were reading, and attended proms and graduations together.

“She was organized to a fault," Dunhour said. “Before she went to bed, she would lay out her clothes for the next day and set the table for dinner.”

When she visited, Mrs. Thompson would bring a jar of homemade jelly as a gift. “We called it Missey jam,” Dunhour said. “She also was a fantastic baker.”

Each March, the two friends made a point of visiting the Philadelphia Flower Show, where Mrs. Thompson toured the exhibits at lightning speed. “We raced through the Flower Show,” Dunhour said.

“She was full of life, and to have that taken away, and at this young age and so quickly, isn’t fair,” Dunhour said. “We have big shoes to fill.”

Born in Philadelphia, she grew up here and in Birmingham, Mich. She graduated from Marion High School, a Catholic school for girls outside Detroit. She spent most summer weekends at her family’s vacation house in Sea Isle City, where she met her husband.

The couple married in December 1990. They had two daughters, whom they raised in Bryn Mawr.

Mrs. Thompson earned a bachelor’s degree in political science and a master’s degree in health administration from St. Joseph’s University. In 1986, she joined City Line Family Medicine as its practice administrator and stayed for 21 years. The physician group sees patients ages 14 and older.

In 2007, she joined the staff at Children’s Hospital as the practice manager of Kids First Haverford and a second Kids First in West Chester. In 2012, she moved on to the hospital’s Philadelphia site as the senior administrative director of the department of child and adolescent psychiatry and behavioral services.

She was credited with improving the patient experience and operating the department efficiently, her family said.

As word of her death circulated, hospital colleagues took to the internet to express their appreciation.

“Missey was very kindhearted, understanding, and always smiling,” wrote Ayeshia Williams of Philadelphia. “I will miss walking with her to meetings, trying to keep up with her fast-paced walking. Missey was truly the best boss that I’ve ever had.”

Outside work, Mrs. Thompson enjoyed sewing, refinishing furniture, reading, biking, gardening, jogging, and making pasta from scratch. She sewed blankets for her daughters, nieces, and nephews.

A volunteer for various charitable causes, she joined in fund-raising walks and runs, as well as public events sponsored by CHOP.

Her favorite place was the Shore. “Missey was happiest when she was with her family and friends in Sea Isle,” her family said. “Whether it was reading on the beach, an evening run, or enjoying a glass of wine on the porch of the little yellow house, she relished those moments.”

Besides her husband, she is survived by daughters Cathrine M. and Meredith R. Thompson; four brothers; two sisters; and five nieces and nephews.

Visitations will be from 6 to 9 p.m. Thursday, Nov. 7, at the D’Anjolell Memorial Home of Broomall, 2811 West Chester Pike, and from 9 to 10:45 a.m. Friday, Nov. 8, at St. Thomas of Villanova Church on the university campus, 800 Lancaster Ave., Villanova. A Funeral Mass will be celebrated there at 11 a.m. Burial is private.

Memorial donations may be made to the Bryn Mawr Hospital Foundation, 130 S. Bryn Mawr Ave., Bryn Mawr, Pa. 19010, or via https://www.mainlinehealth.org/ways-to-give/bryn-mawr-hospital-foundation/types-of-gifts.