The `Machete` actress - who had an on/off romance with the DJ until April 2009 - is said to have been in constant contact with her former lover since leaving rehab last month.
A friend of the troubled star told Life and Style magazine: "Lindsay and Sam started speaking as soon as Lindsay got out of rehab. They text constantly. It turned into something more, and they`ve secretly hooked up."
The DJ regularly visited Lindsay while she was undergoing a drug rehabilitation course at the UCLA Medical Center following her 13-day prison stint for violating her bail conditions of a 2007 conviction for driving under influence.
However, while the 24-year-old actress now claims to be sober, onlookers are said to have spotted Lindsay partying until the small hours at New York`s Boom Boom Room on Saturday night (11.09.10) - just 18 days after being released from the rehabilitation facility.
An insider told US Weekly magazine: "It`s the same old circle of lying and denials. She`s telling everyone she didn`t go out. We`re like, `Lindsay, people saw you there!`. It looked like she didn`t want to be noticed.
"Everything that she went through seems not to have changed her a bit."