The 24-year-old is ordered to appear before a Beverly Hills judge Friday to answer for a failed drug test – the penalty being a possible 30 days behind bars.
"She's scared she might have to go back to jail," says a source. "This is a wake-up call for her in a way. In the past, she dismissed everything, never took it seriously and now she's like 'Oh [expletive], something bad could happen.' "
The actress reportedly tested positive for cocaine as well as amphetamines recently. But experts say Superior Court Judge Elden Fox could order more rehab for Lohan in lieu of jail.
"Judge Fox is a compassionate judge who might choose to help her with her addiction versus just punishing her with jail," says L.A. criminal defense attorney Steve Sitkoff, who's not involved with the case.
But according to the Lohan source, a third stay at the all-female-inmate facility could be just what she needs.
"Her true friends are actually happy this is happening," the source says. "They never knew what it would take for Lindsay to listen. This might be it. But still, the attitude of some of her friends is, 'Oh no, not again.' It never ends with her."