For those who ever thought that Broadway librettists Betty Comden and Adolph Green were married, it's an easy mistake to make. "When I first saw them, I thought they were married, too," admits Phyllis Newman, the real Mrs. Green.

Seated on a plushy purple velvet armchair in the lobby of the Clift Hotel, Phyllis Newman is a study in chic. And she is definitely festive, especially when she cracks that heart-shaped grin that has lit up Broadway and television for the past 25 years.Her book, "Just in Time," subtitled "Notes From My Life," (Simon and Schuster, $18.95) recently hit the stands, and she's hit the road to do a little publicity. Mostly, the book is a collection of bits and snatches of personal history coupled with torrents of feelings and impressions having to do with her two breast cancer operations and the aftermath.

The autobiographical parts of "Just in Time" (also the title of a song written by her husband and Betty Comden for "Bells Are Ringing") are a fascinating story of a kid star. And an honest outpouring of one famous woman's experience and emotion vis-a-vis breast cancer.

Phyllis Newman was born in New Jersey to Rachel and Sid Newman. Her mother was a carnival fortune teller and her father was a jack-of-all-trades (mind reader, trainer of Puffy the World's Only Hypnotizing Cat, hat designer, voice teacher) who was filled more with enthusiasm than ability. Young Phyllis was beauty-laced-with-chutzpah, gifted with a piquant face, a brilliant smile and a fairly big voice.

When she met Adolph Green and his crowd, she realized that they were special. First of all, they were a "different generation," she says, admitting that she "never expected to marry older. The guys I went with were my age. But it happened. He was the man I fell in love with."

Adolph Green was already established as a hit-producing Broadway showman. While his friends numbered the Leonard Bernsteins, the Charles Chaplins, and Lauren Bacall, her friends were "young, funny and not famous."

Green's crowd was also the one that made Broadway glitter in the '50s and '60s - the folks who could ultimately hire Phyllis Newman for such roles as stand-by for Judy Holliday in "Bells Are Ringing," the part of Jane in "First Impressions," a short-lived but charming musical based on "Pride and Prejudice," or her smash Tony-winning Martha Vail in "Subways Are for Sleeping" in which she played most of her scenes wrapped in a towel.

"You bet it dawned on me who these people were," she says. "I guess I never felt like I caught up with them. I married into one of the most accomplished groups. Not like they are jet setters who are rich, but they know so much. By the time I met them, they had already been enormously successful and gifted in what they did."

But, says Newman, while she "learned to be friends with them, I bent over backwards not to use them. I tried to pursue my own thing."

Through the years, Newman had been able to combine a varied and fun career - she was a regular on "That Was the Week That Was" and "What's My Line"; she became the darling of the talk shows, especially Johnny Carson, and she starred in two one-woman shows, "I'm Getting My Act Together and Taking It on the Road" and "The Madwoman of Central Park West" - with her life as wife and mother. Then the roof caved in.

When she was diagnosed with breast cancer in 1983, her first reaction was: "Fear. Stark terror. You sort of make these scenarios in your head when you hear those words," she says, her mobile face tense with memory. "You sort of wait for it. I was aware. You mentally try it out: `Breast cancer.' Then you hear it and you can't believe it. I knew it was coming. And now, it's here. I was talking like that to myself."

Unlike many women who go through mastectomy or lumpectomy operations, Newman says that she stayed pretty much to herself. Refusing to go into any support group, she opted for individual therapy.

"I was afraid of not feeling unique," she comments. "This was my tragedy. Nobody was going to go through it but me. It didn't matter that I was on the floor of a hospital that was solely women with breast cancer and that I had to go to daily exercise classes with other women. I mean, I had to. I would have preferred not to. I would have liked to exercise in my room. I wanted to feel that it was my own personal tragedy and nobody but me was going through it."

Newman has gotten through the past five years. Tough years. Years in which she pushed herself, perhaps too hard, to get back in harness for Broadway and television.