Yeah, Supes himself has said it. So has Calculator.
Supes was also eating her dust when they flew thru space...he couldn't even find her when she turned on the "jets." She was also able to hear Calculator (who was on Earth, or at least on a satellite far away from her location) when she was fairly far away from Earth.
Yeah...it was crazy. She was in space and Calculator's satellite was spying on her. He saw her dust Supes and was like "Who is this girl?". Supergirl then turned in his direction and glared.
Calculator was like "WTF...could she have heard me? Impossible". He then quickly turns off the surveillance equipment (smart move).
When Kara got back to the Fortress she told Batman & Supes that they weren't the only ones keeping an eye on her.
I'm hoping that Batman tells Superman how to get to this "next level" of power...or at least explains why Kara seems to be more powerful than Supes.
Well I saw this comic or the one before it and the ship that Supergirl came from space was supplying her with the sunlight before she went to earth and I also remember hearing Superman always held back in his fight to prevent himself from killing people and that he can here clouds scrape together and squeeze coal into diamonds. Supergirl would win this fight.
Shes not stronger then him he said she may be, they are still not sure yet. Supes was following her in space, Kara already new he was but she amp her speed up and lost him; Supes (even though he wasn't trying to race her) even lost her with telescopic vision.