The goalkeeper was the hero of one of the biggest nights ever in Australian sport, making three saves on Saturday to help the Matildas to a 7-6 penalty shootout win over France and into the Women's World Cup semi-final against England.
For Arnold, who only became first-choice goalkeeper in Feburary, it capped off her incredible rise from third choice at the Tokyo Olympics to Matildas hero.
Post-match, she revealed that she'd been unwell for both the round-of-16 win over Denmark and Saturday night - but was "never" going to miss either.
"I will remember this night for the rest of my life," she said.
"I definitely haven't processed it.
"That is the craziest game I've ever played, considering what was on the line.
"It's going to take a long time to really realise what has happened and what I've done and what the team has done. I'm just super proud to be Australian right now.
"I haven't been too well in the last couple of weeks. So I'm still getting over that, hence the eyes - this isn't tears, yet, it's not tears.
"You've just got to do your job. I was always gonna play."
Arnold made several clutch saves during regular and extra time to ensure Australia reached a penalty shootout.
But then she really made her mark, denying Selma Bacha, Eve Perriset and Kenza Dali.
"I think I do have an instinct, and I tend to just trust my gut," she said.
Arnold then had the chance to earn victory when charged with the responsibility of taking the fifth penalty kick herself - but she "sliced it" onto the post.
"Clearly I wasn't thinking much," she joked.
"The girls are singing my praises, but I'm seriously so proud of each and every one of them especially after I missed the penalty as well and seeing them rally around me like they did to keep me in the game."
The rollercoaster kept on coming.
At 6-6, Arnold denied Dali and thought she'd just made the biggest save of her career
VAR showed Arnold had come off her line, which has been cracked down on even further under recent rule changes.
It meant Dali got another chance to score - but Arnold denied her again.
Three spot-kicks later, Australia were through.
"It was a bit of a mind game to be honest, whether she's gonna go the same way or change it up but I backed myself and thankfully I got the save again," said Arnold.
"I switched it up between my technique and the new technique and it looks like it works."
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