She brought home four gold medals from the indoor event in Poland last month, one for every event that she participated in.
Despite this, she says the games made her more nervous than any of her past events.
It was her first time competing in an indoor arena and she had injured her leg while training two weeks before the competition.
She says an indoor arena was a challenge because of the rule that a competitor isn't allowed to touch the lines between lanes and the indoor track was at an angle.
"It was a really big worry because if you touch the line, you're disqualified and of course the track goes up and around like a cycling track (slanted)," says Marcia.
She was nervous about potentially having to run on the outside slanted lane and set about practising before her event started.
Three Dutch competitors explained how to go about manoeuvring the slanted track, "as you get to that area, go as fast as you can and the downward speed once you make the top will keep you in the lane".
Luckily, she did not draw that lane in any of her races.
Petley competed in the women's 90-year-old category winning gold in the 60m sprint, the 200m run, the weight throw and the hammer throw.
"At 90 I'm damn lucky to be able to run," was her comment on how the games went for her.
Marcia recalls the highlight of the event being how formal and efficient the event was.
Being indoors allowed for a more formal presentation than the outdoors would be able to hold, there was a large screen showing the event, time/distance and country.
It even allowed them to play the national anthem which was a new experience for Petley and something that happened four times, and all of them had her thinking the same thing.
"I didn't know what to do, should I cry or laugh or what I should do. All of these strangers standing in front of me snapping pictures," she says.
Petley had previously said that this was going to be her last games before retiring from athletics.
But with a 2020 Masters happening in Toronto, and her daughter offering to help get her there, Petley says she may lace up her shoes for competition one more time.