The actress, who should be on a promotional trail for her new Netflix film Rebecca, was due to attend an event for Hollywood Foreign Press Association on Tuesday - but backed out last-minute, according to a new report.
The latest news comes days after she dropped out of Friday's upcoming episode of The Graham Norton Show and the Today Show.
WATCH: Lily James stars in new Netflix movie Rebecca
Last Monday, Lily was the talk of the town when pictures emerged of her kissing her Pursuit of Love co-star, Dominic, in Rome. The actress has yet to speak out about the photos.
Dominic, who married film producer Catherine FitzGerald in 2010, and Lily, 31, were openly affectionate with each other.
Since the photos came to light, Dominic has put on a reunited front with his wife Catherine, and told press: "I just want to say our marriage is strong and we are very much still together." The couple also handed out a piece of paper that bore the same words and contained both of their signatures.
Lily is yet to release a comment following those pictures
Dominic and Catherine share four children, and originally dated at university before rekindling their romance after Dominic broke up with his girlfriend Polly Astor, with whom he shares a daughter. In June 2010, the actor married Catherine in her native Ireland.
Lily, meanwhile, was in an on-off relationship with her boyfriend Matt Smith, who plays a young Prince Philip in The Crown. The pair dated for five years before officially splitting this year.
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