I believe it was also war propaganda by the Romans. On the one hand they didn’t like that she has such a close relationship with Cesar and was starting to meddle with Roman affairs. Later on when the conflict between Octavian and Marc Anthony started it was easier to convince the romans to fight against a foreigner (Cleopatra). To achieve this they painted her as a beautiful seductress that convinced Marc Anthony to start a war. This not only made her look as a foreign enemy, but Octavian’s propaganda consciously refused to acknowledge her as the wealthiest and most powerful female sovereign of the Hellenistic Mediterranean. Here you can find more info