How do you write the name Estelle in Greek?

There isn't a direct Greek equivalent of the name Estelle. Estelle is of French origin, ultimately derived from the Old German "stella" meaning "star."

To translate the meaning, you could use a Greek word meaning "star," which is αστέρι (asteri). However, this is a word, not a name. You could potentially create a name based on it, like Asteria (Αστερία), which is already a Greek name, though not directly related to Estelle. But it captures the meaning.