I don't think she had any clothes to change into in Kim's car. I think different people are just using different words to describe the same thing, and simply not choosing their words carefully
Her outfit at the hos[ital is described as a red nightgown. If it's the same clothes, the only thing I can figure out it that the person describing it as "nightgpwn" must be a guy and he thinks it's baby-doll pajamas.