Zatanna Zatara
Daughter of the famous stage magician and escape artist Zatara, Zatanna joined him on tour as his assistant when she was a teenager, and also became good friends (as well as possessing a crush) with his student "John Smith" (actually Bruce Wayne during his training to become a crime fighter).
After her father's death, Zatanna became a talented stage magician in her own right. For the finale of a show in Gotham City, she made the contents of the Gotham Mint disappear, to show up magic debunker Montague Kane. Unfortunately for her, Kane had not only seen through her trick, but was a thief, and stole the money while framing her for the crime. She was freed from custody and assisted in bringing Kane to justice by Batman, whom she recognized as her friend from long ago. When the adventure was concluded, Zatanna disappeared in a puff of smoke; leaving behind a note written on a handbill from her show wherein she acknowledged that she remembered him as John Smith. She expressed her sadness at the course his life had taken and told him not to forget to write.
Sometime later, she developed or discovered genuine magical powers, which she used to aid the Justice League, and occasionally sprinkled in with her normal stage tricks. It also became apparent that at some point, she found out Batman's real name as Bruce Wayne (whether he told her or she discovered by other means is unknown). After Wonder Woman was turned into a pig by Circe, Batman approached Zatanna for help, and she assisted him in tracking Circe down and reversing the spell.
During Darkseid's last invasion of Earth, Zatanna was one of many League Members called to help fight the invading Apokoliptian forces, and afterwards to pursue and capture the remaining members of the Legion of Doom.
Many years later, an elderly Bruce Wayne included her among a small group of women whom he remembered as special to him.