Thinking back to the afternoon when she said Mr. Arias had grabbed her, Dr. Arce said she regretted not having fought back. She was in shock, she said. She had first met Mr. Arias through her mother, a former legislator in his party, and had visited his house with her mother in the past.

“I just froze, and I didn’t know what to do,” she said in an interview. “I was so much in shock. That had never happened to me before.”

Dr. Arce said the only thing that occurred to her at the time was to cry out: “You’re married!”

She said she made up an excuse about having an appointment at the National Assembly and hurried out. She was in such a panic, she said, that she actually went to the National Assembly, even though she had no meeting scheduled.

There, Dr. Arce met a member of Congress she knew and told her what had just happened, she said.

That legislator’s aide, who did not want his name published because he did not wish to get entangled in a scandal involving such an influential person, confirmed the account to The Times. The aide said Dr. Arce had been teary-eyed and nervous.

That same day, Dr. Arce also called her boyfriend, who lives in France, and told him.

“I immediately trusted Alex,” the boyfriend, Jean Marie Collin, said in an interview. “I never had a doubt about what she told me.”

Dr. Arce also said she told her brother, her father, and several other people in the nuclear disarmament movement. Her complaint says she spoke to 15 people. One of those people, with whom Dr. Arce shared the story during the meeting in Vienna, told The Times that Dr. Arce had been in tears when she spoke about it.