January 11, 1999 12:00 PM

On the last day of her fight against a rare form of cancer that devastated her petite, five-foot frame, actress Michelle Thomas whispered a special endearment to her former boyfriend, actor Malcolm-Jamal Warner: “Elephant juice.” Mouthing those words, explains Warner, 28, who had flown to New York City from Los Angeles to be at her bedside, “looks like you’re saying, ‘I love you.’ That was always our thing. When I saw her, I said, ‘Elephant juice.’ She smiled and said, ‘Elephant juice.’ ”

On the following morning, Wed., Dec. 23, Thomas, who most recently starred as duplicitous vixen Callie Rogers on the CBS soap The Young and the Restless, died at age 30 in a private room at Manhattan’s Memorial Sloan-Kettering Cancer Center. At her side were childhood friends and family members, including her father, musician Dennis “D.T.” Thomas, 47, a founding member of the long-running R&B group Kool & the Gang, and her mother, actress Phynjuar Thomas, 47. “It ravaged her just like that,” says Phynjuar, whose daughter had spent the previous day watching videos, listening to music and hanging Christmas decorations in her hospital room, along with photos of Michelle’s Yorkshire terrier Mitzy, which she had named after the character her mom played alongside her in several episodes of Family Matters. “Michelle was sitting up laughing and talking,” says Phynjuar. “She was walking around the ward. She was planning on being home for Christmas morning. The next day it was all downhill. She went incredibly fast.”

Steeped in show business from an early age, Thomas, who was born in Brookline, Mass., and raised in Montclair, N.J., with her brother David (now 25 and an aspiring musician), attended her mother’s regional theater performances as a child and often accompanied her father on Kool & the Gang concert tours. “They are all her uncles, her true family,” Phynjuar says of her husband’s bandmates. “This has devastated the group.”

By 1983, Michelle was appearing in TV commercials and five years later landed the role of Warner’s girlfriend on the NBC smash hit The Cosby Show. “Malcolm was the love of her life,” says Phynjuar. “I think he was her only real boyfriend.” The couple’s off-screen relationship continued after Michelle left the show in 1990 and joined, for five seasons, the cast of Family Matters as the eventual love interest of star Jaleel White’s character, Steve Urkel. “She spent a lot of her career playing girls,” says Warner, who remained friends with Thomas after the two broke up in 1994. “The wonderful thing about The Young and the Restless was she finally got to play a woman. She finally got to be sexy and to show people that there was more to her than Justine from Cosby.”

A lifelong vegetarian who neither drank alcohol nor smoked, Michelle was diagnosed in August 1997 with Intra-abdominal Desmoplastic Small Round Cell Tumor, a form of cancer usually found in adolescent boys. Confident of full recovery after doctors in Los Angeles removed a lemon-size tumor from her abdomen, Michelle landed her Restless role last spring. Then, in October, she underwent emergency surgery when a second cancerous growth ruptured. “With all these stitches, she gets on a plane and came home for Thanksgiving,” says Phynjuar. “She got in my bed and stayed there. There’s something magical about a mom’s bed.”

“I’m sure she was in pain, but we never knew it,” says her lifelong friend and publicist Kahdijah Bell, the daughter of Kool & the Gang’s Ronald Bell. “She kept cracking jokes trying to keep everybody happy and hopeful and in good spirits.” The day after Christmas, Thomas was buried in Montclair following a Muslim funeral service, as she had requested. “She was really fighting that disease with all her heart,” Bell adds. “She wanted to live.”

Steve Dougherty

Eric Francis in Vermont and Ken Baker in Los Angeles