Source: Bang Showbiz NewsKaty Perry appears to have mended her friendship with Kristen Stewart.The 'Part of Me' singer - who reportedly supported close pal Robert Pattinson and encouraged him to move on after the 'Twilight Saga' hunk was left devastated when Kristen cheated on him with married director Rupert Sanders - was spotted celebrating her birthday with the 'Snow White And The Huntsman' actress on Friday night (19.10.12).A source told gossip website Just Jared that the popstar donned a 'Twilight' style vampire costume to celebrate with Kristen and a number of other friends including on-again boyfriend John Mayer at a Los Angeles costume party in The Magic Castle ahead of her 28th birthday on Thursday.The event marked the first time Katy and 22-year-old Kristen have been spotted together in public since the cheating scandal broke in August and reports hinted that Katy had sided with Robert prior to his and Kristen's reconciliation.A source previously said: "Katy has been trying to be as supportive as she can for Rob. She understands what he's going thru and wants to help him. Katy has been urging Rob to go out and be silly and have fun!"Robert (26) was not present at the bash where Katy was seen cosying up to her boyfriend John who she reunited with last week just days after dumping him for failing to commit to their relationship.The singer divorced comedian Russell Brand earlier this year but her younger brother David Hudson, who was also at the party, isn't convinced she has found true love yet.He recently said: "She deserves a true gentleman and I don't think she has found that yet."She needs a man who is changing the world like she is."