Very early in the film, her brother dreams she is walking towards him, wearing a dressing gown.
St Trinians alumni Juno Temple goes all-out on the nudity front for this movie, as the virginal and somewhat slow-thinking Dottie.
The rear nudity is brief and in shadow, but the front view is clear and sustained.
(Shortly before this, we see her lying and then sitting up on her bed, wearing a t-shirt and panties; no nudity as such, but very sexy.
For the record, Ms Temple is quite short and pleasingly rounded, with medium-sized breasts and and a full (dark) bush.