Even for her — even for anyone — Friday night was simply too much.
The human heart is not designed to survive a battle as engrossing and dramatic as the show that Federer and Millman served up.
It pushed her right to the limit.
Mirka was feeling the pinch as early as the second set when her husband made a dramatic comeback to equal the contest at one set all.
She was seen biting her nails and hiding her face.
Her raw discomfort was the talk of the tennis world even in the middle of her husband's rollercoaster battle.
It was only a taste of the torment that was to come as Millman turned the match on its head by sending it into a deciding fifth set at 6-4 6-7 4-6 6-4.
"Mirka is working hard. It is a battle," Aussie tennis great Todd Woodbridge said as vision of Mirka was shown during Channel 9's broadcast with the game on a knife edge at 2-2 in the fifth set.
Tennis legend John McEnroe perfectly summarised Mirka's ordeal by describing the very last point of the contest, where Federer hit a clean winner after a marathon 17-shot rally.
"I don't know how many people in the building were breathing during those 17 shots," he said.
"Couldn't have been many. What a cliff-hanger."
In the end the only feeling that mattered was the sheer euphoria of pressure-releasing victory — which she got to taste when Federer produced a miracle to come back from 8-4 down in the fifth set tiebreak to win 4-6 7-6 6-4 4-6 7-6 (10-8).
There was an even warmer feeling just a few minutes away for Mirka when she was finally able to embrace her husband after he walked off court feeling every minute of his four hours on court.
Mirka has made a habit of making headlines around the world for the waves of emotion she is forced to endure watching her husband play.
On Wednesday night she was spotted taking photos of Federer with her mobile phone on Rod Laver Arena as he charged through his second-round match.
Mirka's touching gesture of capturing the photos of her husband just like any other wife watching her husband play sport resonated warmly with sports fans around the world.
