Didn't it bother anyone else that Mulligan was way too old?

I believe Mulligan is a very good actress but the overwhelming love for her in this particular movie always surprised me.

When I watched the movie I kept thinking "here is a 25-year old woman acting like a 16-year old who is trying to behave/appear to be an adult". Simply didn't work at all. Usually miscasting agewise is not that big of a deal for me but when the entire premise is based upon a young girl playing grownup but an adult is playing the role, my ability to suspend disbelief went out the door.

It turned out Mulligan wasn't quite 25. She was 22 and 10 months at the start of production, which is still 6-7 years older than the character.