The photos were taken by Duchess Kate Middleton before the princess left for Willcocks Nursery School.
The source also described her as 'so polite, but also fun and energetic, ' adding, 'She has lovely manners'.
"She's very sweet and very confident - she's always chatting away", an insider reveals to the publication.
At the time, the Duchess of Cambridge confessed she was trying to teach Charlotte Spanish too, so the young Princess has caught up quickly in less than a year.More news: President Trump expected to unveil proposals during Nashville speech
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Royal watchers once again pointed out just how much Prince George's younger sister takes after her great-grandmother, The Queen, in the looks department. Her older brother, Prince George, attended preschool at Westacre Montessori School in Norfolk.
And a source tells the magazine that she really is as cute as she looks.
Charlotte will be a full-time pupil at the school.
Princess Charlotte joins her big brother Prince George in mastering some of the basics of the Spanish language, as Kate revealed on a visit to Wick Court farm in Gloucestershire past year that Prince George could already count to ten in the language.
A source told The Sun: "She might not be three until May but they were convinced she'd love it and so far she has".