Jenny Boyd had a front row seat at some of the most pivotal moments in music in the Sixties and Seventies. Take the year 1968. A successful model, she traveled with the Beatles to Rishikesh in India to receive spiritual tuition from Maharishi Yogi (her sister, Pattie Boyd, was married to George Harrison). Later that year she was with John Lennon’s wife, Cynthia, when they returned to the Lennon family home in Surrey to find John playing host to Yoko Ono.

Just to add to the rock-royalty credentials, Boyd at that point was the girlfriend of Fleetwood Mac’s co-founder Mick Fleetwood, whom she met while at school when they were both 16. It was a stormy relationship, to put it mildly. They eventually moved to California, and married and divorced twice.

Fleetwood Mac struck gold with the multimillion-selling album Rumours in 1977. Los Angeles in that period was like a Jackie Collins novel, with booze, drugs and infidelity by the bucketload. Boyd was in the thick of it, the ultimate rock-star wife. “Oh, I was no angel,” she says. “I was at the party — just not to the extent that they were, thank God. Would I be here if I had been?”

It’s a good question. Still, she balanced looking after her two young daughters with Fleetwood while catering to his demands. “It was chaos,” she recalls. “I know some of the girlfriends of the band members were seeing psychiatrists three times a week. They couldn’t hack it. And the Seventies is where cocaine comes in. There’d always be this big bag of it. Coke is evil. There’s something so destructive and hard about it.”

Los Angeles in the 1970s was like a Jackie Collins novel, with booze, drugs and infidelity by the bucketload. Jenny Boyd was in the thick of it, the ultimate rock-star wife.

How does someone survive that world? Plenty don’t, of course. Boyd, traumatized by her experiences, eventually swapped the high life to retrain as a psychologist. It’s a fascinating life story, as detailed in her memoir, Jennifer Juniper, which is what we meet to talk about at the modernist London flat Boyd shares with her third husband, the architect David Levitt.

Boyd, 75, is elfin, warm but watchful, her eyes twinkling with mischief and, sometimes, with tears. She is just back from visiting Fleetwood in Maui. They are in mourning for Fleetwood Mac’s keyboardist and singer, Christine McVie, who died in November, aged 79. “It’s heartbreaking and unbelievable,” she says. “There’s a gap in the world. A hole. She was such an important part of our lives. We were a family.”

Boyd remains close to Pattie, her sister. “We were chatting only yesterday, reminiscing about it all.” There’s a lot to chew on, not least the marriages to multiple rock musicians — Pattie eventually left Harrison for Eric Clapton, Jenny went on to marry the King Crimson drummer Ian Wallace — and both women took years to extricate themselves from relationships mired in addiction and dysfunction.

From left, John Lennon and his first wife, Cynthia, travel from London to India with George Harrison; his sister-in-law, Jenny; and Pattie Boyd, Harrison’s first wife.

During one of many breaks from Fleetwood in the Seventies, Boyd returned to England with her children, renting an idyllic cottage in Surrey. There was a catch, though: Clapton and her sister were near neighbors. Parties at Clapton’s house were “incredibly wild”, not exactly child-friendly. But that duality was a fact of her life: motherhood on one hand, mayhem on the other. “That was what I knew; there’d been years of that. You don’t think anything of it. You don’t think, ‘Ooh, I’m on a Learjet.’ Or someone says, ‘You were with the Beatles in Rishikesh.’ But you don’t think, ‘I’m sitting with the Beatles,’ because you’re in the present, you’re young, you’re having your hands hennaed, hanging out in the sunshine; everything’s cool.”

The trip to India ended badly, when the Maharishi was accused of making sexual advances toward the actress Mia Farrow. “It was very sudden,” Boyd remembers. “George knocked on my door and said, ‘Come on, Jenny. Pack your things.’ I suspect now that John was keen to get back to Yoko, although we couldn’t know that at the time.”

“I know some of the girlfriends of the band members were seeing psychiatrists three times a week.”

Of the infamous encounter with Ono, Boyd says: “My main memory is of John lying on this chaise longue, with me at the other end where his feet were, and Cynthia in the kitchen. And John just wiggled his toes and said, ‘Hello, Jenny’, like he just didn’t care. He was like a naughty little boy.”

Again and again, you’re struck by this mix of the mad and the mundane. But for Boyd these people were simply her friends. When Keith Moon and Ronnie Wood popped round to her LA home for dinner, Boyd just remembers thinking about the food. “The main thing that was anxiety-making was my worry that I wasn’t a very good cook,” she says, laughing again.

Before the excesses of the Seventies lost their appeal, Fleetwood Mac and their entourage had a ball, Boyd emphasizes. But the drugs took a toll on her relationship with Fleetwood, who was spiraling ever downward as the band’s sales soared. “You’re looking for this person all the time,” Boyd says. “You know he’s in there, but you don’t know how to cope with living with someone who’s an addict. And the entourage are enablers, worshippers.”

Having finally fled from Fleetwood in 1978, Boyd fell headlong into the arms of Wallace, only to find herself trapped once again in a relationship bedeviled by excess in which she was, as before, expected to play the role of helpmeet. An epiphany finally arrived in Hawaii in the late Eighties, when she, Wallace and a group of musicians that included the American blues singer Bonnie Raitt went swimming. Some of them had taken magic mushrooms, and Boyd came close to drowning.

“I’d been given a chance,” she says. “I didn’t drown. It was life-changing. I thought, ‘Where have I been for all those years?’ And a bell went off.”

On her return to California, Boyd enrolled on a master’s course in psychology and spent 20 years working at addiction treatment centers. Talk about insider knowledge. Her distance from the past allows her to forgive, if not to forget. A difficult, sometimes traumatic childhood equipped her and Pattie for the rock-god world. “We knew about chaos. And rock and roll is just the same because they’re all children.”

She remains firm friends with Fleetwood. “There was never a time where I thought, ‘Ugh, I hate him.’ We’ve always had that closeness, and I don’t think anything could ever erode it.”

It’s Harrison whom she remembers with great affection. “We had a real bond. I have this strong memory of Pattie, George and I hugging. It was this feeling that we knew we were all on this journey, and that things had changed from the happy-go-lucky early Sixties to a sense of ‘what’s this all about?’” His sage advice to her is threaded through her book. “Just be yourself,” he’d often say. And, albeit belatedly, Boyd decided to do just that.

Dan Cairns is a music editor and features writer for The Sunday Times