Lohan has been accused of violating her probation in a necklace-theft case by lying to police and driving recklessly when she crashed her Porsche into a truck last June.
Lawyer Shawn Holley entered the plea even though Lohan reportedly hired a new attorney and had him draft a letter firing Holley Monday.
TMZ said it is unclear if Holley has received the letter yet.
Asked if she was still representing the 26-year-old starlet, Holley told the judge hearing the case Tuesday, "At this point, yes."
"The representation issue will be nailed down," Holley promised.
Lohan has been ordered to appear at a pretrial hearing Jan. 30, TMZ said.
The former child star of hit films such as "The Parent Trap" and "Mean Girls" has seen her career eclipsed in recent years by her legal woes and battles with drug and alcohol addiction. She was most recently seen in the critically panned TV movie "Liz & Dick."