Lorena Marquez is her name. She was a girl who lived in San Diego, then when part of the city sunk, she was one of the people who became a part of Sub Diego. It was revealed that by using Aquaman's D.N.A. a scientist poluted the drinking water of San Diego and then arranaged the sinking of it.
Lorena is unique when it comes to the residents of Sub Diego, since she is the only one who can survive on land for any amount of time. Lorena made an impression on Aquaman and start to become his liason with the people of Sub Diego, and eventually adopted a costume and the name Aquagirl.
In the beginning of Teen Titans #34 Lorena was on the team with Speedy, Hawk, Dove, Zatara, and a kid that looks like Plastic Man's son Luke. Aquagirl and Hawk were arguing over powers and usefulness on the team, it seems they both share very strong personalities. We also know that during that year a character named Miss Martian was also on the team. During the arc of "Titans Tomorrow," she was shown as an adult along with the rest of the team. It was revealed that she has been a member for years, and had a close friendship with Ravager before her and the current Titans parted ways.
It's possible she may join the Titans. If not perhaps she may end up with the new East team....