The 25-year-old singer's mother Andrea found the fans in the crowd after they posted their story on Instagram, reported E! online.
"Some of you may have saw on facebook that Chris and I plan to get married in 3 days at the Taylor Swift concert," Katy wrote on Instagram.
"We originally planned a a whole wedding for 12-13-14 (Taylor's 25th birthday!) We had reasons why we had to put it off. Meanwhile, I have had a gown hanging in my closet!
The day after the concert, Katy posted the picture of herself and her husband Chris meeting Taylor backstage.
"Instagram, meet my new husband Chris and our new friend Taylor! I have no words to express last night!! My two dreams came true!" she captioned the picture.