Society sisters Paris and Nicky Hilton are experiencing some major sibling rivalry.

Spies at Avenue nightclub's two-year anniversary party in New York City recently spotted newly single Paris with her old sidekick Nicky —and one party-goer told In Touch it was obvious that Nicky was less than thrilled to be back in the club scene with her party-hopping sister. "Paris kept poking her and asking Nicky over and over why she was being so 'lame,'" says the onlooker. "In front of all their friends, Paris called Nicky 'boring' and 'lame' numerous times throughout the night."

The spy adds, "Nicky finally snapped back," telling Paris she was "annoying" and "rude" before storming out. The harsh words continued, with Paris telling friends that she and Nicky have been going at it “a lot lately." She even complained that she wanted "a separate hotel room for the night so she could be away from Nicky!" says the source.

The sisters’ younger brother Barron Hilton has also been confiding to friends that he is “sick of hearing about his sisters’ fights." He even admitted that his sisters "have too much animosity towards each other" and went so far as to say "they won't ever be friends again!"

Barron “knows they hate each other" one insider confesses to In Touch. "But he doesn’t want to hear about it anymore from either of them. He thinks they are so fake." Too bad they didn't save some of this bickering for their reality show — it would have probably made for better ratings!

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