From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Chu-Li (FUNimation "Chuu Lee") was a girl who lived at the foot of Mount Goro-Goro. Son Goku met her during his three years training under Kami. She saved Goku after he was struck by lightning and lost consciousness.
Chu-Li kept a baby bird named Pippi as a pet and doted on it. One day, Pippi went somewhere far away. As Chu-Li waited for its return on the roof, she simply sensed when it came back even though Pippi was not seen or heard. From this, Goku learned the art of sensing someone's presence, something that would be useful in the future. She has never been seen since.