I'm thinking that this might have happened in the episode in which Lucy and Kevin get married...

Ruthie comes down the stairs, all dressed up, ready to go to the wedding...and Eric sees her, and he's just stunned at how beautiful she looks...

And then Ruthie says to Eric, "I know...I look grown-up, don't I?"

When I saw that scene, I thought, "Actually Ruthie, you don't look grown up at all...you look like an 10 or 11 year old that's playing dress up...wearing a fancy dress doesn't automatically make you look "grown up"."

Ruthie was a little too full of herself in that scene...

I halfway expected her shoes to be 5 sizes too big....just like a little kid playing dress-up...