Rimell started training at the historic Kinnersley yard in Worcestershire in July 1981 following the death of her husband, the legendary Fred Rimell, and saddled Gaye Brief to Champion Hurdle glory at the 1983 Cheltenham Festival.
She retired from training in the late 1980s, but continued to be involved in racing and was the owner-breeder of Simon, who was from the dynasty that produced Gaye Brief and ended up running in two Grand Nationals.
Mark Rimell said to Press Association Sport: "She had a great life and passed away in peace this morning.
"She was a great woman and left her mark in a great sport.
"She had a very successful and a very good life.
"There is no point in being sad about it. We should celebrate her."
Mercy Rimell also saddled Gaye Chance to victory in the 1984 Stayers' Hurdle at the Cheltenham Festival and won the Arkle Trophy three years later with Gala's Image.
The John Spearing-trained Simon was regularly ridden by Andrew Thornton, who said Rimell was "wonderful woman".
"I had ever so much time for Mercy," he said.
"She was straight down the line, to the point and direct - and that's what I loved about her. If you didn't like it, tough.
"I always used to visit her and you could guarantee, even at 98, she would be dressed in her finery - with rings on, her jewellery on and her make-up on.
"She always wanted you to see her at her best, and I'm sure that's how she'd liked to be remembered.
"I didn't ride for her for about seven years after Simon and then Barton Gift, who she jointly-owned and bred, came along and he was my 998th winner at Bangor last December.
"I remember one time she came up to me about Barton Gift and said, 'Andrew, is this horse any good?', and I said that he was, but he needs time.
"And then Mercy said to me, 'Andrew, time is something I don't have!'.
"That just typified Mercy and her sense of humour. She was a wonderful woman."
Mark Rimell, who is now a trainer, added: "She taught me an awful lot. I looked up to her and admired her greatly.
"We only saw her on Sunday for lunch and she was in good form, as normal, and passed away peacefully.
"She will be sorely missed by us all."
