antecedents - Personal pronoun before noun?

1. 
   

   Before Sarah can board the bus, she needs to get some coins for the fare.

   
   


2. 
   

   Before she can board the bus, Sarah needs to get some coins for the fare.

   
   

My questions are:

• 
  

  Between the above two sentences, which is more correct?

  
  


• 
  

  Can the pronoun come before the noun?

  
  


• 
  

  Is there any rule defining this issue?

  
  


• 
  

  Also, must the noun only be in the main clause?