Responses
No, because if someone finds out that she DOES have blonde hair and blue eyes and she has been hiding then it’s contempt against the church.
As a Duke's daughter, she is fairly well known, so her family would be in big trouble for hiding a blond, blue-eyed woman. But if she openly becomes a nun half a year prior, nobody can blame the family, and she can not be drafted.
Wouldn't cutting her hair short, dyeing it other colour and keeping it properly under the head-cloth help her to hide better ??? It's always a mystery why people on the run keep their original look intact..