A WOMAN WHO had planned to talk voluntarily last week with special prosecutor Arthur Christy claims that she has now changed her mind after a Carter -- Mondale reelection official told her: "Stay cool, do nothing, the investigation isn't going anywhere."

Cynthia Alksne, 20, is one of three women who were guests of White House cheif of staff Hamilton Jordan and other Carter Administration insiders at a party in Beverly Hills on Oct. 22, 1977, where cocaine was allegedly sniffed.

Alksne told The Washington Post that she had been invited to dinner in New York last Wednesday night by Joel McCleary, who now runs the Carter campaign in that state. He "wanted to talk," she said.

After talking with him, she had decided against getting involved voluntarily in the Jordan investigation.

McCleary said Friday that Alksne had not told him that she was considering talking to Christy.

"All she asked me was where I thought this thing was going and I told her no place," he said. "That's my personal understanding of what is happening."

McCleary said he told her "there's no sense worrying, there's nothing there."

Alksne, an 18-year-old University of Southern California freshman at the time, attended the party as a guest of John Golden, who was then deputy treasurer of the Democratic National Committee and is one of Jordon's oldest and closest friends.

Alksne told The Washington Post last November that she had not seen Jordan or Golden use cocaine, but had been offered the drug herself as soon as she arrived at the party, and had turned it down.

She was also invited by Golden, she said, to join him and Jordan and Carter pollster Pat Caddell and two other women later at their hotel, the Century Plaza. Golden identified one of the women to Alksne, she said, "as a pro, a prostitute, from Vegas."

The White House has produced witnesses to deny allegations by the party's host, industrialist Leo Wyler, that the Jordan entourage had brought "drugs" and "loose women" into his home that evening.

Alksne, daughter of a prominent neurosurgeon in La Jolla, interrupted college last fall to work for Sen. Edward M. (Ted) Kennedy's campaign in key primary states from New Hampshire to Illinois.

She told a reporter who found her four months ago that she was aware her motivation could be attacked as political if she told her story to Christy. At that point, it was unclear if Christy intended to expand his investigation beyond the cocaine-sniffing allegations centering around an incident at Studio 54 in New York.

Attorney General Benjamin R. Civiletti had recommended when Christy was appointed that the inquiry by limited only to Jordan's visit to Studio 54.

But the judge who appointed Christy instructed him to investigate not only the Studio 54 charges but "any other related or relevant allegation" that Jordan violated the federal law against possession of such durgs. Alksne decided, after conferring with her parents during a visit at Christmas, to wait for Christy or the FBI to come looking for her. When Christy and two of his staff turned up in California last week to interview potential witnesses for a grand jury later this month, Alksne sent word to Christy that she would be in touch with his New York office last Thursday or Friday.

Although she is not working on Kennedy's New York primary campaign, she is staying currently in a borrowed apartment in Manhattan, because it is too late to return this year to her prelaw courses at UCLA. Kennedy's campaign is "over" for her, she said.

Alksne told The Washington Post that she had been contacted in Chicago recently by McCleary, who asked to set up the Wednesday dinner. In 1977 he was treasurer of the DNC and present at the Wyler party early in the evening. He was not part of Jordan's group and left early.

Alksne said she has known McCleary since she was 16. They met at a political convention in 1976.

Alksne was invited to the Wyler party, she was told The Washington Post in a series of interviews, because Golden sometimes dates one of her closest friends, Judy Bagley, who works for the Carter -- Mondale Committee in Washington

Bagley was not in California the night of the Wyler party, according to Alksne, so she went alone to meet Golden.

Jordan, Golden and Cadell were already there, she says.

"The first thing anyone said to me after I walked through the door," she recalls, "was when a youngish . . . thirtyish . . . man with sandy hair . . .in a blue suit . . . a man I've never seen before or since . . . walked up and asked me if I'd like cocaine -- making a snorting gesture with his fingers and his nose -- the same way you would ask someone what they'd like to drink."

She declined, she says, and asked where she could find John Golden.

"I knew I was way in over my head from the first minute," she says. "I had just barely turned 18. I kept thinking I've got to get out of here."

According to Alksne, Golden invited her to come back with them to the Century Plaza when the Wyler party broke up. She declined.

She went to a phone and called a cab. When it arrived, she says, Golden climbed in beside her and "commandeered " the vehicle for himself and Jordan and Caddell and the women with them.

The driver was instructed by Golden to take the party to the Century Plaza. Once there, Alksne says that she swithched to another cab and went home.

A few days later, Alksne reported the events of that evening to a friend of her parents. She also wrote a detailed account, accompanied by a floor plan and with a diagram of where people were standing or sitting during the party, in a diary she has been keeping since she was 14.

Attempts to reach Golden over a period of several days last week unsuccessful. A White House press spokesman declined to take questions for him because he is "a private citizen."