Here's why:
* The Ptolemaic dynasty was Greek: The Ptolemies were descendants of one of Alexander the Great's generals, Ptolemy I Soter. They ruled Egypt after Alexander's death and maintained a Greek cultural identity.
* Greek was the official language: The Ptolemaic rulers used Greek as the language of administration, education, and high society.
* Egyptian was a language of the people: While Egyptian was still spoken by the majority of the population, it was not considered the "official" language of the ruling class.
* Cleopatra was multilingual: She spoke Greek, but also learned Coptic (the late stage of the Egyptian language), likely for practical reasons.
It's important to remember that while Cleopatra was the last active ruler of the Ptolemies, she was not the first. The Ptolemaic dynasty ruled Egypt for almost 300 years, with many pharaohs before Cleopatra. It is unlikely that any of them were fluent in Egyptian.