Ashlee and Rumer: New BFFs?

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They say you should keep your friends close and enemies closer.

That may have been the case Saturday night at the grand opening of newest Hollywood hotspot Central, when Ashlee Simpson was seen partying with Rumer Willis — an odd couple with a common bond, Pete Wentz. Before the mascara-wearing Fall Out Boy star began dating Jessica's younger sis, gossip columns linked him to the the eldest of Demi Moore and Bruce Willis' children.

But, on this night, with the rocker MIA, it was all water under the bridge, a source tells OK!. The girls bonded over rock music and girl talk.

“They danced together the whole time,” an eyewitness tells OK! “If there was any jealousy over Pete, it’s certainly gone. They seemed like best friends.”