According to WWD.com, the Smile hitmaker was seen at the Chanel headquarters in Paris yesterday waiting for a wedding dress fitting.
Lily, who is due to marry long-term boyfriend Sam Cooper this year, allegedly said she was there to see Karl for her wedding gown.
Allen was signed up by Karl in 2009 to star as the face of Chanel's Coco Cocoon handbag line, and the pair have been friends since.
Today she was pictured on the front row at the Chanel autumn/winter 2011 show, which was held at the Grand Palais in the French capital.