Marie and the Trio can be heard on a Cranford Publications CD of digitally remastered 78 and LP recordings by The MacLellan Trio. These are wonderful old recordings in which older playing styles and tunings and intonations are easily apparent.
A wonderful interview with Marie is in the book "A Cape Breton Céilidh" compiled and edited by Allister MacGillivray. Much of the information here is paraphrased from there.
Marie was raised in Riverside, Inverness County. As was common in musical homes in those days, there was a foot pumped parlor reed organ in the house on which she learned to play as a girl. She eventually was good enough to take over as organist in her Catholic church while still a child. She learned to read music, and she says she learned to play melody by working from the hymnal.
Her father, Big Ranald, taught her about chording. When they would play together, he would call chords out to her as well as directions - up and down. According to Marie, her mother Maryann was the only person of her generation to accompany fiddlers.
Marie also tells that when they would go to dances in those days there were neither piano nor organ in the halls, so she would accompany fiddlers on the guitar, which she says was "tuned in the Hawaiian styling and played with a bar". (Interesting idea - it would be fun to hear a CB fiddler accompanied today with a pedal steel guitar).
She left home and moved to Sydney at the age of 23 and one of her dreams was to own a piano. She found work and managed to buy one, and took lessons from Bernie MacIntosh. In Sydney she was able to work with Joe MacLean, Winston Scotty Fitzgerald, Angus Chisolm, Johnny MacLean, and Billy MacPhee.
There weren't that many piano players working at the time but she does recall listening to and picking up ideas over the years from Lila Hashem, Margaret and Dougie MacPhee, Mary Jessie MacDonald, and Janet Cameron.
She makes the common lament that oftentimes the piano player is completely overlooked, despite being integral to the sound. She says, "the violin is a beautiful instrument but without a piano it's like a bell without a toungue!"
In the book "A Cape Breton Céilidh" compiled and editted by Allister MacGillivray, Marie goes on at some length about the specifics of accompanying the fiddle on the piano. It is quite interesting and detailed and for that page alone, it is worth buying Allister's book.