For Memorial Day 2013, Katy Perry kicked off summer with a few good friends -- including John Mayer. Two months after their second breakup, the "Shadow Days" troubadour, 35, was among the guests at Perry's brand-new Hollywood Hills home on May 27 for a barbecue bash, Us Weekly can confirm.
Whether the reunion signals a full-on reconciliation for the pair remains to be seen. "They seem to be back together -- or back together-ish," one observer tells Us of Mayer and Perry, 28. "They were very flirty and having a really good time together. They have good chemistry."
Adds another witness: "They were definitely friendly."
Other revelers for Monday's party included Girls star Allison Williams and boyfriend Ricky Van Veen -- who double dated with Perry and Mayer at the Grammys in February --- plus Mindy Kaling, BJ Novak, 2 Broke Girls' Beth Behrs, Raising Hope's Shannon Woodward, plus actresses Kate Micucci and Riki Lindhome.
Us broke news of the pair's second split in mid-March; the twosome began a casual romance during summer 2012 and briefly called it quits in August before reconciling that September. (The "Teenage Dream" singer and Russell Brand finalized their divorce in early 2012.)
"It's not over until it's over," another confidante told Us in March after Perry and Mayer's second split. "You have to see how things play out."
This article originally appeared on Usmagazine.com: Katy Perry, John Mayer Reunite, Flirt at Her Memorial Day Party