"One: To her the glass wasn't half full, to her, it was always overflowing," he said, repeating comments he made during her eulogy. "And two, she didn't wear her heart on her sleeve. She wore it like a jacket."
Friends said Ms. Steinberg had a contagious smile and a way with people that made the shortest interactions memorable.
"Everybody that has met her just kind of left a conversation with her feeling energized," said Travis Larrabe, one of her former teachers at Penn Charter.
A natural public speaker, Ms. Steinberg was a sports announcer for the Dartmouth radio station, an interest that led her to an internship with ESPN. Though she had expressed an interest in becoming a sports broadcaster when she finished school in 2015, she had more recently been looking into jobs in financial services, her father said.
Ms. Steinberg also loved Camp Walden, a girls' summer camp she attended for seven years with her sister and mother, Sidney Steinberg said. In the fall, Ms. Steinberg was looking forward to her sister joining her as a student at Dartmouth.
"She and her sister Leigh, they absolutely, they could not have adored each other any more," their father said.
Her passion inspired others.
"There wasn't a day where Blaine came to practice without a smile on her face," said Tori Small, Ms. Steinberg's lacrosse coach at Penn Charter. "She was the kind of kid who was constantly trying to make herself better. But not just herself ... all the players around her, too."
A Facebook group was created over the weekend to remember Ms. Steinberg, and more than 1,000 people had joined by Monday. Many former teammates and friends posted memories and shared pictures of Ms. Steinberg. One showed Ms. Steinberg as a little girl with her soccer teammates, holding trophies and smiling.
"Everyone was touched by your positive attitude, amazing smile, constant upbeat personality, and incredible athleticism," said the comment below the photo.
In addition to her father and sister, Ms. Steinberg is survived by her mother, Jill.
Contributions may be made to the Main Idea at Camp Walden, 180 E. Prospect Ave., No. 178, Mamaroneck, N.Y. 10543, or the Women's Legacy Fund at William Penn Charter School, 3000 W. School House Lane, Philadelphia 19144.