Yes escribir is a reflective verb.A reflexive pronoun (pronombre reflexivo ) is used as part of a reflexive verb (verbo reflexivo ) to indicate that someone or something is performing an action on or for itself.
 
        
             
        
        
        
The singular form is una libreta
        
             
        
        
        
Answer 
La chica hablaba por el teléfono con su novio