Why? It's not that Clydebank-born Rafferty is ever less than kind and concerned. But she is also the acting equivalent of Zelig. She's everywhere. In everything. Continually. On stage, she's made more appearances than a rep theatre dining table. She's been in almost every Scottish television drama except Four Feather Falls.
And to compound the unrelenting pain of others, Rafferty's range is wider than Wyoming, from everywoman roles in the likes of Hamish Macbeth and Dr Finlay, from High Road to River City.
Indeed, after rehearsing her drug-addled prostitute part with Raindog Theatre in the early 1990s, the actress would then point a sparkly pink shoe in the direction of Glasgow's King's Theatre - and shine as the Fairy Princess.
Now, at 63, the carousel hasn't stopped spinning. Switch on the television soon and you'll see Rafferty return as the wonderful (in)human cockroach Ella Cotter in Rab C Nesbitt. Right now, she's not only Grandma Mainland in new CBBC series, Katie Morag, she's currently starring in cracked American dream classic drama True West, at the Citizens' Theatre in Glasgow, playing Mom to Alex Fearns.
Clearly, the lady has major talent. But why such continual success? Does she need it as badly as an X Factor contestant?
"Oh yes," she admits over coffee at the Citz. "I've always wanted to act since I can remember when my mother (Betty), a cinema usherette, introduced me to the movie world. When I saw the old films I became desperate to become Bette Davis and wear floaty dresses and have a maid travel with me."
But how to become a Bette? Growing up in Clydebank, Rafferty had no female role models. "I did have one," she corrects. "Deborah Kerr was from Helensburgh. And I was always encouraged by my parents. My dad came to everything I was in and beamed."
Barbara Ann Brown, as she was, beamed confidence from an early age. At 13, she joined the local am-dram outfit, Clydebank Rep, playing a cockney sparra alongside Ian Tough, who'd later became a Krankie. "When I was 15, I wrote to the producer of BBC drama This Man Craig and said I'd love to be in the show. And he put me in three episodes alongside other child players, Alex Norton and Brian Pettifer. I had this immense desire to show off, I guess."
And to adventure. Aged 16, she answered the Sits Vac ad in a newspaper; Elderly Parisian Millionaire Widower Desperately Seeking English Teacher For Two Teenage Boys. Rafferty got the job after claiming to be a 22 year-old fluent French speaker.
But on arrival, she realised she'd been hired as a 'cure' for the widower's son's assumed homosexuality. The Sixties dolly bird didn't become conversion medicine in cami knickers however (her young charge was just a late starter), but the Millionaire Widower liked the bold young Scot and sent her to study at the Sorbonne. "I told the snooty girls there that my father was in shipbuilding. They thought I meant he owned a shipyard."
Back home, still super-charged, Rafferty joined a drama group in Glasgow where she teamed up with young hopeful David Hayman and they'd go to the Citizens' Theatre to watch plays. During her drama college stint (where she met her future husband, Peter) the super-keen young actress travelled with chums to Edinburgh to see Olivier's Shylock, and gained an audience with.
"We were allowed into his dressing room," she recalls of meeting the legend, the excitement of the day redolent in her voice.
"His braces were down and he smelled of gin, although it was witch hazel, used to remove make-up. He spoke to us for ages and kissed us on the head. And he had the bluest eyes you have ever seen."
On leaving college, the very determined Rafferty landed a role in cult film classic, The Wickerman. And her career trajectory was set to rocket.
But . . .
"I got married, and in 1972 I had a daughter, Amy," she recalls in serious voice. "I planned to carry on working, but somehow I lost my confidence. I did a play at the Close Theatre in Glasgow, Les Justes, and while I got great reviews I didn't think I was good enough. I felt if I couldn't get the absolute honesty of the character, that I was rotten, that I was acting at being an actor. And I came off the stage shaking."
Confidence and rampant self doubt are often actors' yin and yang. They need confidence to go on stage. They (ie, the good ones) need rampant self doubt to make them internalise, to get to the soul of their character.
A few years back, when she auditioned for Baroness Bomburst in Chitty, Rafferty thought nothing of bursting into song in the producer's office - the full Ethel Merman - then hitching up her smart French suit to "just above the decency line" and declaring "I could look great in a basque, by the way".
Yet, for this feature, fear and self doubt surfaced when asked the simple panel questions below; it took a day for her to think about 'best trait'. 'Greatest influence' had to be left out because she didn't want to leave anyone out. A need to be universally loved? You bet. And she won't criticise a single production she's ever been in. Self-protection?
It wasn't until the late eighties, another two kids later (Nick and Bob) and stints working in the civil service and in a wine bar, that Rafferty was teased back onto the stage. But the kids were an obstacle.
"Director Morag Fullerton cast me in a schools tour, and my confidence came back. It also meant I could be home at night. But I remember Nick giving me a hard time about working until I got round him saying, "You know how you want to become a fireman? Well, I've always wanted to be an actress." He understood."
It was pal Elaine C Smith who suggested Rafferty for the life-changing role of Ella. "Joining Nesbitt was wonderful," she says of the series, which is back with a special this year. "The characters became so iconoclastic, and it also opened the doors for the big pantos."
She had little trouble finding "the truth" of her sitcom character, a woman so dark she makes Dracula seem like an Ibiza sun worshipper.
"It's in the writing, but I also knew her," she says, grinning. "I had a landlady like her when I was at college, with the scary make-up, the beehive and the voice. I could tap into her."
Indeed. Once, on holiday, while trying to relax by the pool, Rafferty found herself being verbally and physically abused by a teenager.
"The final straw was when he hit me with a flipper. Then as he came to get the flipper back, suddenly I sat up and I felt Ella appear inside me. And it was her voice that came out of my throat when I found myself staring hard at him and saying "If you dae that again son, a'll stab ye!""
Since Nesbitt appeared 25 years ago, Rafferty's career has continued to soar, appearing in countless theatre productions and films such as The Last King of Scotland with James McAvoy. And the other actresses out there probably winced a little on hearing Rafferty's set to star alongside Elaine C Smith in Cinderella, in Aberdeen this Christmas.
Life however, hasn't passed unvisited by great sadness. Rafferty split from husband Peter and he died six years ago. "I still think about him every day," she says in soft voice. She has since found "incredible love" however with actor husband Sean Scanlan, the couple living in Glasgow's West End.
And for the most part, fortunately, the overcoat of self-doubt can be discarded. "When I was 50 and doing The Steamie I went to see a musical theatre coach and she preached to me; "Give it more, Barbara. You've got to be better than the next person". I'm a naturally shy person so I've got to work up the confidence, to act as though I have it."
Because she has to act?
"When I'm not working I'm not . . . " her voice trails off.
"Yes," she says, softly.
True West is at the Citizens Theatre, Glasgow until Saturday November 16. Full information at citz.co.uk