AFAIK, there's considerable debate whether she was physically exceptionally beautiful or not, but to me the important bit about her is this (from https://en.wikipedia.org/wiki/Early_life_of_Cleopatra_VII):

In contrast, Cleopatra could understand and speak multiple languages by adulthood, including Egyptian, Ethiopian, Trogodyte, Hebrew (or Aramaic), Arabic, the Syrian language (perhaps Syriac), Median, Parthian, and Latin, although her Roman colleagues would have preferred to speak with her in her native Koine Greek.

She was the first (only?) Ptolemic ruler who bothered to learn Egyptian. In my book that makes her incredibly attractive!

And consider this: Julius Caesar was no inexperienced youth when it came to women (some details here: https://www.history.com/news/5-things-you-might-not-know-abo...). Mere beauty would not have been enough to impress him that quickly.