General description:
* Comment est-elle ? (This is the most common and literal translation)
* Quelle est-elle ? (This is less common and more formal)
Personality:
* Quel est son caractère ? (What is her character?)
* Quelle est sa personnalité ? (What is her personality?)
* Comment est-elle en tant que personne ? (What is she like as a person?)
Appearance:
* À quoi ressemble-t-elle ? (What does she look like?)
* Comment est-elle physiquement ? (How is she physically?)
The best choice will depend on the context of the conversation.