Probably kicking herself right now.
She generally makes good choices, but no matter how you look at it she's probably kicking herself for turning down Carol now. I read that Rooney Mara was initially interested but turned it down, then Mia came aborad and eventually dropped out only for Mara to come back again. That's funny because I think there was a similar rhythm in the casting process of Sils Maria, another role she probably regrets not doing.
But actors making regrets is so common they're probably used to it, so she'll move on.
It's an ordinary high school day. Except that it's not.