The cutoff for being able to say this in a movie?

So I’m watching the ‘Nancy Drew’ movie which is from 2007, and at one point this girl says “I didn’t get the memo about the party being a retarded theme.” which I thought was hilarious but at the same time I was like “Oh no she didn’t!”.

I know it’s a movie and you can say whatever the heck you want in it, but this is like a G rated movie intended for kids and with the especially politically correct society we live in now, I was surprised by this considering the circumstances!

I’m guessing they wanted to include it in the movie because it’s something a realistic teenager might say.

I don’t really know what I’m asking here, maybe your thoughts on political correctness in movies nowadays or information you know about the time cutoff for when we started getting really picky about what words are acceptable to use? Just any thoughts or discussion?