Why not? Isabelle lives in France and says Bachelot's considered to be kind of an idiot and a self-aggransizer. I'm not sure about in Brazil, but here in the US just because someone has been in government doesn't prove they're not a fool, or don't perhaps think they're impervious to consequences. Here is exactly what she said: “On sait que sa fameuse blessure où il avait été arrêté sept mois est certainement due à un contrôle positif. Quand tu vois un joueur de tennis qui s’arrête pendant des mois, c’est qu’il a été contrôlé positif.†I think everyone can read that. She's merely speculating. Drawing a conclusion based on his injury lay-off. She neither says nor implies that she has proof or has seen any.
It's possible that she thought slandering Nadal re: doping was a minor tennis-related sport and she was just joining in the "fun." She did fail to notice, however, that people don't normally do it publicly, or if they do, they don't accuse him, or anyone else, directly. It does make you question her judgement.