When the new Wonder Woman took over the mantle from her predecessor, she announced that her name was Donna Troy. Many people felt this was a false name, but she uses it in situations where being called Wonder Woman seems awkward.
Speculation as to where she came from is constant. She has been said to be another Amazon from Paradise Island, a holographic projection of Wonder Woman as a young girl (patently false), Wonder Woman's daughter, Wonder Woman's sister, a young baby Wonder Woman found in a fire and trained, and one of the Greek Gods, perhaps Artemis, come to mingle with humanity.
None of these are true.
In 1951, Clark Kent married Lois Lane. Two years later, Lois was pregnant. The trauma of carrying a part-Kryptonian fetus almost killed her. In fact, without Paula Gunther's Purple Healing Ray on Paradise Island, Lois would probably have died several times. Her daughter was born on Paradise Island, and raised there by the Amazons, so it could be said that Laura Kent is an Amazon by birth, if not ethnicity.
Eventually, Laura came back to Man's World and was "adopted" by her real parents. While not as powerful as her father, she is certainly well above human levels and made an excellent successor to her "aunt", the original Wonder Woman.
The new Wonder Girl is indeed Wonder Woman's daughter. During their time together in the Teen Titans in the late 70s, Wonder Woman and Flash III (Wally West) had a liaison that resulted in the birth of Cassandra Troy. Now Cassie follows in her mother's footsteps. However, she does it a lot faster, since she also inherited the Flash family connection to the Speed Force. Of course, as a quarter Kryptonian, she is not as naturally strong and fast as her mother and grandfather. But she does have Amazon training.