Lili began her story by explaining to her followers that she was searching for a basic app to resize her photos (not the content of her photos) when she came across the BodyTune app.
"This morning I was looking for an app that would help me resize my photos to better fit Instagram...And then I came across this app".
Lili - who plays Betty Cooper on Riverdale - then screen recorded the app's ad, which shows you how to slim down different parts of your body which is all kinds of wrong and damaging.
Lili did not hold back her criticisms on her Instagram Story, urging her followers not to use these kinds of apps, as well as calling BodyTune 'hazardous'.
"This is not okay. This is why people develop eating disorders. This is why social media has become hazardous to our health. This is why people have unrealistic expectations of their bodies."
"I implore you: do not use these kinds of apps. If you photoshop your body you are adding to this problem."
Lili continued: "This is how unrealistic standards of human bodies have been created - to the point where people alter their bodies surgically to achieve unattainable results.
"We are better than this. Looking 'skinnier' in a photo on Instagram is not worth the detrimental psychological effects that these photoshopping apps have given our generation."
Lili finished by writing: "Our bodies should not conform to 'one size fits all'.
"People who use these apps and alter their bodies are clearly suffering from low self-esteem, body dysmorphia, or other mental health problems.
"My heart goes out to those people who feel like their bodies aren't good enough.
"But please don't encourage this behaviour".
Say it louder for the people in the back!
If you, or anyone you know is struggling with an eating disorder, please contact the following for help:
Butterfly Foundation at 1800 33 4673
BeyondBlue at 1300 22 4636