"Sam wanted to distance herself from Lindsay when they split up," a source tells PEOPLE. "But Sam never stopped caring. She genuinely cares about Lindsay and just wants to see her get better."
Since Lohan was sentence to 90 days in jail, Ronson has stepped back into the actress's corner.
On Monday, she Tweeted in Lohan's defense against cruel comments made by Joan Rivers. The pair were also spotted dining in L.A., and Ronson has visited Lohan twice at the sober-living facility where she's staying – including a visit Thursday night when she was seen leaving at 4 a.m.
Ronson, who the source says "is sober," wants to help lead Lohan in a better direction. "She gets it, she knows what Lindsay is going through and she knows she needs good people around her helping her down the right path," the source says.
In the coming days, Lohan will need all the support she can get. A source tells PEOPLE that once she reports to jail next week, she'll be kept in a cell at Lynwood jail by herself and have limited access to other inmates, but won't get any special treatment.
She "is not to be given any extra sheets, clothing, towels, etc.," the source says. "She will follow every rule and policy of the facility."
The source also says Lohan will serve no less than 23 days, and possibly more if she violates any rules.
Reporting by JENNIFER GARCIA