IN HER OWN international social circles, Pamela Churchill Harriman is acknowledged one of the great beauties of the 20th century, admired by many of history's richest, most famous and most powerful men.

Mrs. Harriman, once married to British Prime Minister Winston Churchill's son, Randolph, was married to theatrical, and movie producer Leland Hayward, who died in 1971.

In "Haywire," memoirs of her step-daughter Brooke Hayward, the portrait project to millions of readers who may never have heard of Pamela Harriman is not exactly flattering.

Nothing about elder statesman W. Averell Harriman's wife, Pamela, will be used in the television movie based on the book that CBS will air in April.

Her lawyers saw to that.

They also intervened to try and stop Hayward from writing an unauthorized "biography" of Mrs. Harriman. At least a warning has been registered by attorney Edward Bennett Williams that his client will sue if such a book is prepared for publication.

According to Hollywood proudcer Michael Viner, whose wife, Deborah Raffin, stars in "Haywire," at least an hour of the four-hour television film had to be scrapped after legal pressure was brought by Mrs. Harriman.

"It was massacred," he said last week. "There is no way any of that portion can ever appear on screen."

Mrs. Harriman has a tiny needlepoint pillow in her yellow drawing room which says it all: "Be reasonable. Do things MY way."

If you liked the love story of "Mo" and John Dean, you're probably ready for the saga of Jeanne and Marvin Mandel.

Jeanne Mandel is a woman who has kept her sense of humor through the trials and travails of a once-powerful husband who still may go to prison for four years if the U.S. Supreme Court does not intervene.

The former Maryland governor's second wife has been quietly working away on the story of her ordeal and is looking for a collaborator to help her put it in shape.

Out in Whiteside county, ill., birthplace of Ronald Reagan, they used to do a booming business with people writing in and paying $3 for a copy of his birth certificate.

That was in the 1950s, when he first went into politics, and people wanted to know if, like most movie stars, he might be even older than he admits.

They still write, perhaps disappointed to get back a certified court document that shows he really will be only 69 on Feb. 6. The only time any of his old official movie press agent's bios can be found to have fibbed about his age was one that took off only a year, claiming he was born in 1912, not 1911.