Nancy Reagan's White House tour and coffee for Raisa Gorbachev tomorrow isn't exactly shaping up as a reunion of long-separated and adoring friends.

They got along well enough in Geneva two years ago, but last year when Mrs. Gorbachev turned up at the Reykjavik summit after everybody supposedly had agreed that wives would stay home, Mrs. Reagan was obviously miffed.

And putting together tomorrow's private coffee wasn't easy, even though it had been Mrs. Gorbachev who asked to tour the White House. When she failed to respond after a week or so, Mrs. Reagan issued what some saw as an ultimatum.

"I sent the letter two weeks ago," Mrs. Reagan said yesterday as she presided over the arrival of the 18-foot White House Christmas tree, "and it got to the point where I had to know to fill in the schedule, so I did say I have to know."

Asked about her impending visit with Raisa Gorbachev, Mrs. Reagan said, "I don't know her very well."

The first lady did add that "she's very nice" although former White House spokesman Larry Speakes, in his forthcoming book "Speaking Out," writes that at the Geneva summit, Mrs. Reagan found Mrs. Gorbachev to be "a dogmatic Marxist who ... shared little of Nancy's interest in child care, fighting drug abuse or other issues of substance."

"You don't like her," one reporter remarked yesterday.

"I didn't read it that way," said Mrs. Reagan of the observation by Speakes.

And what will they talk about this time when they sit down for coffee? Democracy, maybe?

"I'd like to talk about the drug situation," Mrs. Reagan said.

Considering her past experience, did she think Mrs. Gorbachev would be interested?

Replied the first lady: "We'll soon know."

Barbara Bush and not Nancy Reagan will join Raisa Gorbachev tomorrow morning for another specially conducted tour, this one at the National Gallery of Art. Providing the commentary will be J. Carter Brown, gallery director, with an assist from John R. Stevenson, gallery president.

A spokeswoman for Mrs. Reagan said yesterday that, contrary to speculation, there never had been any plans for the first lady to accompany Mrs. Gorbachev on her sightseeing rounds.

Anatoliy Dobrynin, the Soviet Union's man in Washington for two decades until he went home last year, picked up the phone in Moscow a couple of weeks ago to call an old friend here: Pamela Harriman, whose late husband W. Averell Harriman once was U.S. ambassador to Moscow.

Could she possibly arrange a meeting, perhaps a luncheon, for Raisa Gorbachev at her home, when the Gorbachevs come to town, Dobrynin asked. And could she invite four or five women "of distinction" to join her and Mrs. Gorbachev and Liana Dubinin, wife of the current Soviet ambassador, at the meeting?

Harriman not only could but did. Instead of a luncheon, however, the get-together is being called "a meeting with a cup of tea" to which she has invited Sen. Nancy Kassebaum (R-Kan.), Sen. Barbara Mikulski (D-Md.), Supreme Court Associate Justice Sandra Day O'Connor, Hanna Gray, president of the University of Chicago, and Washington Post Co. Chairman Katharine Graham.

And the meeting's subject?

"Open dialogue but private," said a source.

Steering clear of stepdaughter Maureen Reagan's remark that Mike Deaver "abused the hospitality and friendship" of the Reagans by writing his forthcoming book, Nancy Reagan said yesterday that she hadn't read "Behind the Scenes: In Which the Author Talks About Ronald and Nancy Reagan ... and Himself."

She has, however, read excerpts of it in the December issue of Life magazine.

In fact, she said she was shocked to read in the pre'cis to those excerpts that Deaver had drunk a quart of scotch a day during his last months in the White House as deputy chief of staff. Deaver, a lobbyist who has since revealed that he is an alcoholic, is on trial for perjury.

"Mike, you couldn't have had a quart of scotch a day," Mrs. Reagan said she told Deaver when talking to him by phone a few days after the magazine came out.

"I didn't," Deaver replied. "I took that {reference} out of the book three times."

And according to Lisa Drew, Deaver's editor at William Morrow & Co., which will publish the book early next year, Deaver did delete that reference. Though cut from the book, in a mix-up of the proofs the passage somehow made its way to Life, Drew said yesterday.

"That was the only error in the Life version," she said