It happened at 5th and York Streets in Philadelphia's Kensington section around 9:00 Tuesday night.
Police say a white or tan pickup truck, believed to be a Ford F-150 with tinted windows, struck Veronica Santiago, a mother of two.
"We just can't believe this is happening. She's a young lady with two kids and they don't even know yet," said stepsister Evy Martorell.
Santiago was taken to Temple University Hospital and pronounced dead.
The family said Santiago was visiting her best friend when she was struck.
"I seen her up in the air. I ran over here and she was under the car," friend Raul Rodrigues said.
Relatives and friends could not hold back the tears as they mourned.
"She was a beautiful girl. She'd take the shirt off her back for anybody," said aunt Mille Fonseca.
Santiago worked at the Drug and Alcohol Counseling Center. Relatives say she graduated from technical school a couple of years ago and was working towards becoming a nurse's aide.
Police say the pickup may have front-end damage and a dent on the passenger side door from a previous accident.
Anyone with information can call Philadelphia Police at 215-686-TIPS (8477) or visit the department's website.