Attorneys for Dawn Bradley filed the lawsuit in Indio, Calif., on Thursday.
Bradley said she was seriously injured when she and Lohan got into an altercation at the rehabilitation center. A spokesman for Lohan declined to comment.
Bradley's attorney Owen McIntosh says his client requires surgery on her wrist because of the injury.
Bradley, who is also known by her married name of Dawn Holland, was fired from Betty Ford Center after discussing the incident with Lohan on camera with celebrity website TMZ.
Prosecutors in Riverside County, east of Los Angeles, declined to charge Lohan with battery.
Meanwhile, in court on Thursday, a judge warned Lohan that she needs to speed up her court-ordered community service or she won't finish in time.
Lohan must complete 480 hours of service within a year to comply with her drunken driving sentence.
The "Mean Girls" star is set to return to court Oct. 19 to update the judge on her progress.