Brief History

Nancy Lu was a member of a rival high school basketball team playing against May Parker (aka Spider-Girl) and her high school team. May noticed that the ball was moving on it's own at certain points in the game and her spider-sense buzzed whenever she was near Nancy. Curious, she followed Nancy as Spider-Girl at witnessed Nancy moving objects without actually touching them. Spider-Girl confronted Nancy, who admitted to have a low-level mutant power of telekinesis. Spider-Girl told Nancy it was wrong for a person with powers to play in sports, as it gave them an unfair advantage over the non-powered-players. Nancy quit her basketball team, and realizing that she had been playing against non-powered players, May quit her basketball team too.
 
Later Nancy transferred to May's high school and the girls became friends until she misunderstood the basketball coach and thought that May was being her friend only to get her to join the school basketball team. However the girls resolved their issues and became friends again. But word leaked out that Nancy was a mutant, and an anti-mutant group of teenagers attacked Nancy's home. Spider-Girl saved her, but Nancy no longer felt safe among humans. She was offered a place with Jubilee and her X-People and Nancy accepted. There she learned how to properly utilize her telekinesis and adopted the codename Push. She teamed up with Spider-Girl as Push to assist in the capture of a kid using a magnetic harness to impersonate Magneto  and her powers were actually strong enough to catch his magnetically hurled projectiles and rip apart his harness.  Afterward, as Spider-Girl's request, Push tried to help another mutant student named Sara Hingle who was being pressured to join Magneta and her group of Evil Mutants.

Powers

Telekinesis: Push can move objects with her mind. At first she was limited to small objects, as mentally moving large objects drained her. However, as she trained with the X-People, she could now lift objects as large as herself with her her thoughts and show no signs of fatigue.   
Flight: By using her telekinesis to lift herself, Push can fly via levitation