OLD GREENWICH, Conn. — Every morning, the petite blonde with the bright red lipstick walks the few blocks from her nondescript condo to the Upper Crust Bagel Company on Sound Beach Avenue, the main drag in this picturesque New England hamlet of 6,600 people.

Just about everyone who lives here knows it’s Ruth Madoff in exile, and they mostly leave her alone.

They know the broad outlines of her fall — how her privileged world exploded in December 2008 when her husband, Bernie, confessed to the biggest Ponzi scheme in history, an $18 billion fraud for which he is serving a 150-year sentence.

Ruth lost everything — her money, social status, husband and her two sons. Mark, the elder, committed suicide in 2010, and Andrew died of cancer in 2014.

Ruth will turn 76 this week, two days before HBO airs “Wizard of Lies,” a dramatic retelling of the fall of the house of Madoff, starring Robert De Niro as Bernie and Michelle Pfeiffer as Ruth.

How does she feel about the film’s release?

“I have nothing to say,” she said when The Post knocked on the door of the 989-square-foot townhouse she rents in this bucolic burg of neatly trimmed hedges, where children wait for the school bus outside beautifully restored shingled cottages, and homemakers in Spandex drive their husbands in Audis and Land Rovers to the Metro-North ­station.

It’s only an hour’s train ride to Manhattan, but it’s a world away for Ruth, who once owned a sprawling apartment on the Upper East Side and mansions in Palm Beach and Montauk.

After her husband’s conviction, Ruth was forced to give up her palatial digs, and was no longer welcome among her socialite friends. Donald Trump, who denounced Bernie as “a sleazebag and a scoundrel without par,” refused to rent an apartment to Ruth in any of his Manhattan buildings as she desperately searched for a place to live, a source close to the ­Madoff family told The Post.

Before her husband was sentenced in 2009, Bernie made a deal with prosecutors. In exchange for giving up most of their wealth — $80 million worth of mansions, jewelry, cars and art — Ruth was allowed to keep $2.5 million.

Ruth took the cash and skipped town.

After briefly living in an exclusive condo in Boca Raton, Fla., Ruth came to Old Greenwich in 2012, to be close to her three grandchildren who live nearby. She lived for two years at 57 Tomac Ave. in a quaint house, built in 1905 and then owned by her son Andrew and his estranged wife, Deborah West, public records show.

“She was a very nice neighbor is all I have to say,” said Mike Worden, who lived across the street from the ­Madoff house.

Two months after Andrew died of a rare form of lymphoma, Ruth was booted from her son’s home. It was sold by West two years later and was recently razed by its new owner to make room for new construction.

Ruth moved from 57 Tomac to the townhouse in the condominium complex called The Gables, where she now lives. The gated community features a heated swimming pool, squash courts, gym and security, although there was no guardhouse attendant when The Post visited last week. A one-bedroom unit was listed for $3,100 a month.

It was here that Pfeiffer reportedly sat in Ruth’s kitchen in preparation to play her in “Wizard of Lies,” the drama directed by Barry Levinson. “She sat in her kitchen and studied her,” a source said.

“I don’t think it would be appropriate to say she ‘cooperated’ with the film,” Levinson told Page Six. “Michelle simply spent a little time talking to Ruth. I don’t think Michelle talked much about the script. It was simply to get to know her — however brief the time spent.”

Neighbors say Ruth mainly keeps to herself in Old Greenwich, where she tools around town in a new silver Toyota Prius.

But mostly she just walks and walks, neighbors say.

She strolls every morning to buy a bagel at Upper Crust but avoids the other bakery in town — Sweet Peas. Last week, the upscale bakery and meeting spot was filled with young women in exercise clothes sipping lattes and surrounded by baby ­strollers.

“Ruth never comes in here because these people are part of her old life, and the ones who lost money with Bernie,” said a woman who described herself as a friend.

Now her new friends are a group of women who are active in church craft sales and don’t get their nails or hair done, said a neighbor who has seen Ruth.

“If they weren’t living in Old Greenwich, you would think these ladies were all homeless,” she told The Post. “Ruth spends a lot of time with them, and I have never seen her dressed up here. She’s always in the same jeans.”

Last Christmas, Ruth helped one of her friends sell homemade crafts at a local church bazaar, the neighbor said.

“It was quite the sight to see Ruth Madoff fetching crafts from a tub ­under the table, and taking in money at the sale,” the neighbor said.

Other neighbors have seen her on brisk morning walks at the nearby beach on the Long Island Sound, and strolling up and down the town’s main street, stopping in at Anna ­Banana, a store that sells children’s clothes, and frequenting the Indulge Salon and Beauty Bar.

“Why can’t she just live in peace?” asked a woman who marched out of the salon to confront a Post photographer. “She has a right to her privacy.”

The beauty boutique’s welcoming attitude is in sharp contrast to Manhattan’s tony Pierre Michel salon on East 57th Street, where for a decade Ruth would go for her highlights in Soft Baby Blonde every six weeks. The owners of Pierre Michel not only barred Ruth from the premises after Bernie was arrested in 2008, but last week they told The Post she’s still not welcome back.

“Unfortunately, many of the clients at the Pierre Michel Salon were victims of Bernie Madoff,” a spokeswoman for the salon told The Post. “While those at the salon are forgiving people, and do not wish more hardships on Ruth Madoff, they have to put their clients first.”

Instead of the $400 she paid to color her hair at Pierre Michel, she now pays between $175 and $200 for highlights in Old Greenwich.

Although Ruth was never charged with a crime, the family was shunned, largely because so many people in their elite social group had invested with Bernie and many lost their life savings. Holocaust survivor and ­Nobel laureate Elie Wiesel, who died last year, called Bernie a “scoundrel” and said his charity lost $15.2 million to Madoff, and his own life savings were wiped out.

‘How do you sleep with a man for all those years and don’t know what he is up to? I just don’t buy the story that she knew nothing, and that she’s had a hard time.’

Ira Sorkin, a lawyer who represented Bernie, argues that Ruth is a casualty, too. “She has suffered beyond imagination,” Sorkin said. “She couldn’t walk out of her apartment to get a cup of coffee without being harassed.”

But victims of the fraud had harsher words for Bernie — and his missus.

“You, Mr. Madoff, have two sons that despise you,” said victim Marcia FitzMaurice in a court statement when he was sentenced in 2009. “Your wife, rightfully so, has been vilified and shunned by her friends in the community.”

The couple’s sons refused to speak to her after their father’s arrest. They claimed that they were never in on the scheme, but wondered why she continued to support her husband, living with him at their Manhattan penthouse for the three months that he was under house arrest between 2008 and 2009.

Ruth Alpern met Bernie Madoff when she was 16 and they were attending Far Rockaway High School in Queens. Both she and Bernie grew up in a middle-class Jewish neighborhood in Laurelton. They married in November 1959 when she was 18.

Ruth, who has been married to Bernie for nearly 60 years, worked as a bookkeeper for him when he established his investment business in 1960. But she has maintained that she didn’t know her husband was running a Ponzi scheme.

The couple had discussed committing suicide, even going so far as to swallow a handful of Ambien and other drugs, after the massive fraud was exposed in December 2008, she told the New York Times.

Her written apology, issued in June 2009 as Bernie was being sentenced, rang hollow to many of his victims.

“To say that I feel devastated for the many whom my husband has destroyed is truly inadequate,” the statement read.

Although she used to visit her husband at his federal prison in North Carolina, she stopped after son Andrew gave her an ultimatum in 2012, according to published reports.

If she wanted to have a relationship with Andrew and her two granddaughters, she would have to cut off her visits to Bernie in jail. Her lawyer, Peter Chavkin, refused to comment last week.

“How do you sleep with a man for all those years and don’t know what he is up to?” asked an Old Greenwich shop owner who did not want to be identified because Ruth frequents her store. “I just don’t buy the story that she knew nothing, and that she’s had a hard time. She hasn’t been through what half the people went through. People committed suicide because of the Madoffs. Please!”

Another shopkeeper wondered where Ruth is getting her cash.

In addition to her new car and regular visits to the hairdresser, another neighbor said Ruth is a client of a ­local pilates studio, where a package of three private classes retails for $255.

But others say that Ruth lives modestly in Old Greenwich. No one could recall if she ate at Le Fat Poodle, the town’s best restaurant. She only occasionally drops off blouses at James Wong Laundry and Dry Cleaners, the owner told The Post.

“She’s a very nice lady,” said owner Cliff Ng. “She doesn’t say a whole lot. She’s on the frugal side and doesn’t wear expensive clothes.”

A patron dropping off her dry cleaning on Friday morning told The Post she feels sorry for Ruth.

“Every time she sees someone who recognizes her, you can tell from the expression on her face that she experiences a difficult emotion but she just keeps on smiling and moving on,” said the patron who did not want to be identified. “She is a gentle soul.”

Others were not so charitable.

“That smile, with those red, red lips!” said another owner. “She has this fake, permanent smile affixed to her face. It really irritates me. It’s ­totally fake.”