Former house cleaner Andrea Lawton changed her plea to guilty in federal court Tuesday as part of a plea agreement on charges involving the theft of a rare bust of Benjamin Franklin from a Bryn Mawr home.

In exchange for her pleading guilty to one count of interstate transportation of stolen property, federal prosecutors will recommend to U.S. District Judge C. Darnell Jones II that the second count against her, concealing stolen property, be dismissed. The bust is said to be valued at $3 million.

The deal means a lower maximum prison sentence for the 46-year-old Lawton. The two counts meant as many as 20 years behind bars. Under the single count she pleaded guilty to Tuesday, the maximum possible sentence is 10 years. She also could be fined up to $250,000 and have three years of supervised release after prison.

Jones set sentencing for March 12.

"We're glad to see her taking responsibility for the crime she committed," assistant U.S. attorney Joseph J. Khan said.

Lawton's court-appointed attorney, Martin I. Isenberg, said his client was "presented with evidence that convinced her this was the proper way to go." That evidence included a statement in which she confessed to the theft.

"She's sorry for what she did," Isenberg said.

On Aug. 24, the day she took the plaster bust, Lawton was angry.

She told Lower Merion Township police she was mad that the cleaning service she worked for had fired her. She wanted to cost her ex-employer business by stealing the item that homeowner George A. D'Angelo had told her never to touch - the bust of Franklin.

D'Angelo, a lawyer, said other missing items included a framed picture of the comic musician Victor Borge and a conductor's baton.

Lawton had an accomplice, she claimed, but she never offered a name.

After learning that Lower Merion Township police had issued an arrest warrant for her, the Philadelphia resident packed up the bust and traveled to Mobile, Ala., where she tried to find a buyer, according to an FBI affidavit.

She seemed to have found one in Maryland. Authorities arrested her Sept. 20 as she got off a bus in Elkton. She had packed the bust, which sustained a crack during the journey, in her bag.

Lawton also is facing charges including burglary and criminal trespass- breaking into a structure - in Montgomery County Court. That case is awaiting a pretrial conference, with the trial scheduled for Jan. 9.

Contact Carolyn Davis at 610-313-8109, cdavis@phillynews.com, or follow @carolyntweets on Twitter.