A 25-year-old Arlington woman, accused of attacking her former boyfriend's new girlfriend while disguised as a flower messenger, pleaded guilty yesterday to breaking and entering and malicious wounding.

Mary F. Prevost, testifying in Arlington Circuit Court during a bond hearing after her plea, said that on the day of the incident, Feb. 26, she was distraught over her mother's death 10 months earlier, a breakup with Robert Hogue after a four-year relationship and work due for a George Washington University graduate course in Middle East politics.

"I had about 1,000 pages on the Arab-Israeli conflict to read; I had an exam the next week. I was about to begin working for some foreign newspapers as a correspondent . . . . I was just getting more and more tense . . . . I didn't go there to kill someone. I just wanted someone to hurt as much as I was hurting," Prevost said, breaking into tears.

"How do you feel about the injuries you inflicted" on Cheryle L. Wallis, Judge Benjamin N.A. Kendrick asked.

"I don't know her; I don't care to ever see her again. It makes me sick, knowing that that happened," Prevost said.

"Do you still have the desire to hurt someone?" Kendrick asked.

"No," Prevost said. "I guess I sort of snapped out."

According to a plea agreement, Prevost will receive a maximum sentence of five years on each charge. A charge of arson in connection with a fire last December at Hogue's house was dropped.

During a preliminary hearing in April, Wallis testified that about 6 p.m. Feb. 26 she opened the door of the South Arlington house where she lived with Hogue to a flower messenger with black hair, a khaki parka and a bouquet of roses.

When Wallis asked who the flowers were for, she said in court, the messenger dropped the bouquet and began slashing at her with a knife.

Hogue testified that he chased and tackled the messenger and in the struggle, "the person's hat came off." It was then, Hogue said, that he recognized the "messenger" as Prevost, his ex-girlfriend.

Wallis suffered cuts on her right wrist and left ring finger, as well as a minor puncture wound in the abdomen. Shortly after the incident, she moved out of Hogue's house, and the two called off their wedding.

Kendrick ordered Prevost released on $75,000 bond on the condition that she go to her family's home in West Orange, N.J., and not return to Virginia before her sentencing July 11 unless her father, Francis X. Prevost, accompanies her.

Assistant Commonwealth's Attorney Arthur Karp argued against releasing Prevost, who has been held in a secure ward at the Psychiatric Institute of Washington.

"She decided she wanted to hurt somebody, and she planned it, and she disguised herself so she wouldn't be caught," said Karp. " . . . The court should say, 'Is there some reasonable chance that she might do it again?' "

Prevost's attorney, Jack Kilcarr, said the incident "was a flash in the pan." He said Prevost acted that day "out of sheer frustration, out of sheer anger . . . and out of sheer depression over what had happened to her during the last 10 months."

Hogue, who testified briefly yesterday, walked out of the courtroom after Kendrick ordered Prevost released on bond.

"I think it's important to note that the danger to the community here we're talking about is danger to an ex-boyfriend," Kendrick said. "I'm not so sure that removing her from this area would not be therapeutic."