When a lady hits a new milestone, she doesn't want to party alone.  She wants all her girlfriends there to celebrate.  So Katy Perry invited some of her famous celebrity gal pals out for the release of her new album Prism.

Sisters Tegan & Sara Quinn feted Katy an a L.A. bash earlier this week.  The duo were also joined by Sara Bareilles, showing that there is no basis to the rumors that Perry and Bareilles were beefing over the similar sound of their recent singles 'Roar' and 'Brave'.  Singer/songwriter Ellie Goulding was on hand, so was country newcomer Kasey Musgraves, and rounding out the photo above was Bonnie McKee, Katy's longtime songwriting partner, who is hugely present on Prism.

I guess there was no room for John Mayer among all this girl power.

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