Cir-El appeared in Metropolis during a heated battle; not knowing her to be friend or foe, Superman took her in for questioning after the battle and asked her about her origins and why she was calling herself "Supergirl". She told him that she was his daughter from the future and genetic scan showed she was in fact Superman's child...hearing this, Lois went berserk on Superman, accusing his him of having an affair...Cir-El then told Lois that she was her mother.
After a second genetic scan it was determined that while Superman was the father, Lois was not the mother. When Superman was declared public enemy #1 by President Lex Luthor Cir-El aided Nightwing, Robin, Superboy, and Krypto in trying to rescue Superman and Batman.
It was revealed that Cir-El was created by Brainiac to serve as a host for the 'YES' Virus. Superman was shown a future where he was attacking the human race for some reason, he was told that the death of Cir-El would prevent this future, Cir-El threw herself into a time portal, erasing the future and the 'YES' virus that created it, effectively making sure she was never born so she couldn't come back and alter history.
Cir-El was brought to the present by Bizarro to aid Kara Zor-El alongside several other Supergirls (Linda Danvers, Silverage Kara, and Power Girl).
-Superstrength: Cir-El has Kyrptonian-level superhuman strength
-Superspeed: Cir-El can run at several times the speed of sound
-Flight: While originally only able to leap 1/8th of a mile, Cir-El eventually displayed the power of flight
-Superhearing: Cir-El displayed the ability to hear sounds from vast distances
-Invulnerabilty: Cir-El is resistant to most physical attacks and energy weapons, like all Kyrptonians she is vulnerable to Kryptonite
-Red Sunburst: Cir-El can fire blasts of red solar energy (the wavelength of solar energy that Kryptonians lose their abilities under) from her hands that strike a target with intense heat and concussive force