From PEOPLE Magazine Click to enlarge
There's one thing Jennifer Grey would like to clear up right away: She is not a dancer.

Sure, she was convincing in Dirty Dancing as she mamboed into the arms of Patrick Swayze. But in real life, she so feared the unrealistic expectations of others that she willingly put herself in the corner-far from the nearest dance floor. "I was an actress playing someone who had never danced before, but I became this iconic dance person," she says of her role in the 1987 classic. "I was so afraid of what people would think, I wouldn't even dance at weddings with my husband."

That was just one reason Grey, 50, had the same answer when Dancing with the Stars producers called her each year to offer her a coveted slot on the popular reality competition: "Not interested." But her ballroom insecurities were just the tip of the iceberg. She was still haunted by a deadly car crash that occurred 23 years earlier-at the height of her fame-and suffering from debilitating neck pain caused by the accident as well as intense survivor's guilt. But after Patrick Swayze's death from pancreatic cancer last September-and a life-altering cancer diagnosis of her own-Grey says she was inspired by her onetime dance partner to take another great leap. "Patrick had an enormous impact on me; he was so fearless," she says. "I thought, 'What if I did take more risks?' "

The result: a Viennese waltz on the Sept. 20 season premiere of DWTS that drew raves from the judges and tears from the woman a generation will always know as "Baby," Dirty Dancing's shy Jewish teenager who comes of age in a Catskills retreat. "Baby is back where she belongs," gushed judge Bruno Tonioli. "I know someone up there is going to be very, very proud of you."

High scores aside, the moment marked another kind of triumph for Grey, who less than a year ago learned she had thyroid cancer while undergoing surgery to alleviate the chronic neck pain. She had been hurting for more than two decades, following a 1987 car accident while on vacation in Ireland with actor Matthew Broderick, her Ferris Bueller's Day Off costar and then boyfriend. The head-on collision left the occupants of the other car, a mother and daughter, dead; Broderick was severely injured. "One minute we're going down the road and music is playing, and the next minute ... it's all different," Grey, curled up on a couch at her L.A. home in sweats and a T-shirt, says with a shudder. "I couldn't be fearless after that." Less than a week later, Dirty Dancing opened.

"I became America's sweetheart within five days of the accident," she says. "The juxtaposition of that deep sorrow, the survivor's guilt ... and then being celebrated as the new big thing just didn't jibe. It didn't feel good to be the toast of the town."

As the movie went from sleeper hit to phenomenon, Grey found herself wishing she could disappear. "The impact was emotional and physical," she says. "My body was never the same, my head was never the same, my ambition was never the same."

And so at age 27, with her career at its zenith, Grey began making "a lot of choices most ambitious people would not have made," including getting a nose job in 1989 that radically altered her appearance. In truth, Grey says, her desire for fame was gone; in its place, "I really felt like I wanted to be a wife and a mom," she says, noting that it nevertheless took her 12 years to find Mr. Right in actor-director Clark Gregg (The New Adventures of Old Christine). The two married in 2001 and daughter Stella, 8, was born nearly five months later. Once Stella came along, "it was very hard to get me out of the house because I didn't want to miss any of it. It was all about family, friends."

Grey spent most of her time nesting with her family and getting involved with Stella's school. But a reminder of that 1987 crash lingered: Over time ligaments that had been ripped in the impact of the crash had degenerated, leaving her with "headaches that lasted four days." In 2007 she admitted to PEOPLE that she'd had a wild youth-"I was just very attracted to that whole world of disco and drugs," she said then-but the grown-up Grey was determined to remain narcotic-free. "I don't like putting drugs in my body, so I tolerated the pain," she says of relying solely on Advil and ice packs for relief.

But once she made the decision to join DWTS (after much encouragement from famous pals like Michael J. Fox and Jamie Lee Curtis), she knew a thorough physical was in order. She hoped the checkup would be a formality. Instead Dr. Robert S. Bray Jr., a neurological spine surgeon in L.A., found Grey's spinal cord was compressed, leaving her neck in such a precarious position that "one slip, one fall, one minor rear-end-that's how close she was to paralysis," says Bray.

It was shocking news to Grey, who had tried to ignore the pain for years. "I was just so grateful I survived the accident, I didn't address that I was in chronic pain," she says. "I always thought I was lucky to have gotten through it."

Suddenly Grey learned her decision to dance would be postponed for at least a year, if not forever: Bray ordered up two spinal surgeries. It was during these procedures that he grew worried about a "lump" in Grey's neck-previously diagnosed as a benign thyroid nodule-and pressured her to have it removed. "Anyone who thinks I'm a plastic-surgery freak is insane. I basically walked around with a goiter for four years because I was so afraid of surgery," she says.

It turned out the growth was now full-blown thyroid cancer-Grey underwent two more surgeries to have her entire thyroid removed. "If that tumor had broken out of the capsule of the thyroid," says Bray, "that's a very bad cancer. She caught it in time."

Now, after four operations, Grey-who has a titanium plate secured with screws in her neck-can hold her head high, literally. The fact that she didn't need radiation or chemotherapy after her thyroid surgery made her even more grateful to turn 50 in March-and gave her a new outlook on her career.

"My daughter is almost old enough where she doesn't want to spend every minute with me," says Grey, who landed a guest-starring role on the Fox drama House (the episode airs Oct. 18). "I met an old part of myself I had forgotten about," she says with a smile. "I thought, 'What if I dared to do something that really, really scared me more than anything?' "

For Grey, that meant putting on her Dancing shoes. Now rehearsing six hours a day, seven days a week, she's embracing "the joy of it," even during the grueling workouts she's enduring with partner Derek Hough (see sidebar).

"It's insane!" she says of rehearsals with Hough. Grey is quick to point out that her partner is 25 and was 2 years old when she made Dirty Dancing. "Because of that, he should go a little easy on me, shouldn't he?" she jokes.

Not that Grey would settle for giving anything less than 100 percent. "It's like I've been starving myself because of what people might think of me," she says. "This is like eating a delicious steak after 23 years of fasting." And in this hard-earned second act, Grey says she isn't worried if she misses a step or two. "If my dancing is a disaster-it doesn't define me as a person," she says. "The only reason I'm doing this is for myself."