The 49-year-old trucking heiress dazzled on the red carpet at a movie premiere with the ex-Beatle, her boyfriend of 18 months.
Two days later, Shevell shielded herself behind a colleague, turning away from cameras recording a Metropolitan Transportation Authority (MTA) meeting where she cast a vote to raise city subway fares 25%.
Few who have seen Shevell photographed in Israel, Antigua and at the Grammy Awards with McCartney know of her other life as an executive at a New Jersey trucking company and board member of the largest mass transit agency in the United States.
But her public and behind-the-scene personas have collided more and more since the socialite began seeing McCartney in Long Island's Hamptons area in late 2007.
Since January 2008, Shevell has missed four full board meetings, more than any voting member, according to MTA meeting minutes reviewed by The Associated Press. She attended one finance committee meeting in the past year, and has 26 absences in total.
Shevell skipped an MTA committee meeting approving a controversial fare hike the day she walked the red carpet in London. Since early 2008, the unpaid appointee has the worst attendance of any voting board member, sometimes missing meetings to travel around the world with McCartney.
"It is significant. The whole point of the board is to be a check and balance on the MTA's staff work, said Gene Russianoff, a New York City mass transit advocate.
"If members can't show up for meetings," he said, "they should resign."
But celebrity observers aren't surprised that Shevell's former private life is taking a back seat to the 66-year-old McCartney.
"Who can blame her?" said Peter Castro, deputy managing editor of People magazine.
"How many of us would be happy at an MTA meeting versus stepping out onto the red carpet at a Grammy event with a living Beatle?" Shevell - who didn't return messages seeking comment for this story - is a vice president of New England Motor Freight Inc, a New Jersey, trucking company owned by her father, Myron Shevell.
She was married for over 20 years to lawyer Bruce Blakeman, a close friend to former Governor George Pataki, who appointed her to the MTA board. TV personality Barbara Walters is her cousin.
But Shevell's public profile barely existed before photographs appeared in late 2007 of her and McCartney on Long Island, where McCartney had previously holidayed with his wife Linda, who died from breast cancer in 1998.
"Nobody knew who she was," said writer Steven Gaines, the co-author of The Love You Make: An Insider's Story of The Beatles.
"She's like 25,000 other accomplished women out here in the Hamptons."
Since then, she's become a red-carpet staple, appearing at the March 23 premiere of The Boat That Rocked in London, fashion shows by McCartney's daughter Stella, the Grammys and McCartney concerts around the world.
The public has largely embraced the love story, especially McCartney fans disillusioned by the ex-Beatle's bitter breakup from his second wife, Heather Mills, said Castro.
"Any person coming after that is going to get a lot of attention and scrutiny, because it's a soap opera," he said.
"They seem to be really in love and just tremendously pleased with each other."
Shevell hasn't given up her work or her unpaid seat on the MTA, the agency that oversees subways, buses, bridges and tunnels for over 8 million New Yorkers. She was appointed in 2001 to a term that expires in 2011. She sits on five committees and chairs one overseeing the agency's $US10 billion ($NZ17.4 billion) in capital construction projects. Most meet every month or so.
She missed a March 23 committee meeting that approved raising a one-way subway ride to $US2.50 because she was with McCartney in London. But she attended the full meeting March 25 that gave final approval to the fare hike, explaining her yes vote as a last resort after state lawmakers failed to come up with enough aid for the cash-strapped agency.
"We do have the responsibility to maintain a safe, high-quality transportation system. Regretfully, without the deserved government funding, we are left no choice. ... And we do plead with those in Albany to do the right thing," she said.
The MTA has defended Shevell's board service. Fellow board member Andrew Albert, who sits near Shevell at meetings, wondered if attention given to McCartney's girlfriend could help commuters by calling attention to the MTA's financial woes.
"It just means there's a few more cameras in the room" at meetings, he said.
