The wife of Representative Duncan Hunter of California pleaded guilty on Thursday to one criminal count in a case in which she and her husband were accused of using more than $200,000 in campaign funds for personal use — including lavish dinners, vacations, private school for their children, and even plane tickets for their pet rabbit.

Margaret Hunter, who has also agreed to cooperate with prosecutors, admitted in Federal District Court in San Diego that she had conspired with her husband to violate campaign finance law.

“I am deeply remorseful, and I apologize,” Ms. Hunter, 44, said through her lawyers, Tom McNamara and Logan Smith. “I have accepted full responsibility for my conduct.” She will face up to five years in prison and a $250,000 fine when she is sentenced on Sept. 16, about a week after Representative Hunter is to go on trial.

Mr. Hunter, who served as a Marine in Iraq and Afghanistan and was first elected in 2008 to a seat held by his father, did not attend the hearing on Thursday. But in a statement, he said that the case was politically motivated.