Explanation:

Carte blanche: complete freedom to act as one wishes, (in piquet) a hand containing no court cards as dealt.
t means that she is free to do or say whatever she pleases. Note that it is a mistake to say “a carte blanche” unless you are talking about a piquet hand or a blank, signed contract. When used in the sense of giving someone free rein, you say they have been given “carte blanche,” and not “a carte blanche.”