If you have a friend:
* Se llama [nombre de la amiga]. (Her name is [friend's name].)
* Mi amiga se llama [nombre de la amiga]. (My friend's name is [friend's name].)
If you don't have a friend or don't want to share the name:
* No tengo amigas. (I don't have any friends.)
* No quiero decir su nombre. (I don't want to say her name.)
* No lo recuerdo. (I don't remember.)
To be more casual, you can use:
* Se llama [nombre de la amiga] ¿y tú? (Her name is [friend's name], and you?)
* [Nombre de la amiga] ¿cómo te llamas? (Her name is [friend's name]. What's your name?)
Remember to adjust the answer to fit the specific situation and your relationship with the person asking the question.