"I'm trying to stay healthy, I'll just get the fries," she captioned the video, claiming she often heard health-conscious customers make the comment before ordering.
"You sure about that?"
The video has racked up more than 5.4 million views, with customers saying the video was definite confirmation that fries weren't the healthiest option.
"Fried food is not healthy ... like seriously," one person commented.
"I'm not having McDonald's again," another commenter claimed.
But other viewers weren't surprised, pointing out that the video was showing the grease trap underneath the fries tray.
@maccaschick also confirmed this, posting a follow-up video, in which she showed the top fries tray being lifted to reveal the bottom grease trap underneath.
"Guys please, these aren't the fries. It's the oil and salt left at the end of the day," she explained.
"It doesn't affect how your fries taste. It's just the residue under the filter after making like 1000 fries."
Despite showing the residue left by the fries, many viewers said it would take far more to put them off ordering fries, with several labelling the grimy residue "good flavour".
A few went as far as to say that they would gladly eat from the bottom tray, which they likened to salty mashed potato.
"I have zero problems with this video," one person wrote.