The 31-year-old reality TV star was spotted with Keibler a number of times last week. Keibler and Clooney have been dating since July 2011.
According to a source, Kardashian and Keibler first bumped into each other at Yankee Stadium last weekend at the Madonna concert.
Kardashian was with Jonathan Cheban, who's also friendly with Keibler, reported New York Daily News.
"They've known each other for years and have always been friendly, just not best friends," a source said.
During the week, the duo also hung out at the Marchesa fashion show in Grand Central Station, which Kardashian attended with Kanye West.