How do I say "is she your sister?" in French?

Est-elle votre soeur?

Thanks! Also, is it okay to say "est-ce que c'est ta soeur?" for "is that your sister?"

Yes. Note that I used the formal form of you, while you used the familiar form.

To say "Is she your sister?" in French, you would say "Est-ce qu'elle est ta sœur?" Here's a breakdown of how to construct the sentence:

1. Start with the verb "être," which means "to be." In this case, the third-person singular form of the verb is used, which is "est" (is).

2. Next, add the pronoun "elle," which means "she."

3. Then, include the possessive pronoun "ta," which means "your" (when addressing someone informally). If you are addressing the person formally, you would use the possessive pronoun "votre" instead.

4. Finally, finish the sentence with the noun "sœur," which means "sister."

Putting it all together, you get "Est-ce qu'elle est ta sœur?" which translates to "Is she your sister?"