Charlotte almost always has a bodyguard. Maybe the writer meant she didn't have her attorney or a relative with her to advise her on certain answers.
I'm not so sure. She always has a bodyguard in public event, porobably to make sure people won't bother her, and when travelling to countries like Brazil, or when been picked up from airports, train stations (then it's kind of a bodyguard-driver) but she's never been seen with a bodyguard in Paris when she goes about her business or in the côte d'azur when she is with friends.
I've seen Andrea a couple of times in Paris (ages ago, when he was going out with the german girl) and there weren't any bodyguards around. Also, if you remember, he's had problems with paparazzi more than once, I remember once in Italy when he pushed one to the floor and once in Ibiza when he was with Maria Jurado and he had to shout to be left alone and paparazzi even where filming inside his car and they weren't any bodyguards at all.
My guess is that the casiraghi have bodyguards in public events and certain places where it is dangerous to be rich, like Brazil, but when they are about their business in Paris, Italy, etc... they are on their own.