The band, which consists of Nathan Sykes, Tom Parker, Jay McGuiness, Siva Kaneswaran and George, partied at The Dream hotel after performing the Jingle Ball gig at Madison Square Garden in New York, reported Sun online.
Lohan was spotted smiling and joking backstage with George and bandmate Parker.
The 26-year-old actress was seen leaving the venue with George while covering her face behind a maroon trilby. She was recently arrested for punching a woman at a pub.
Lohan's most recent woes also include a 145,000 pounds tax bill. She has been arrested six times, in rehab five times, jailed and completed 536 hours of community service.