so i wrote a letter of interest to the PD of my number one program.  she wrote back with nice words.  i wrote her back.  she wrote me back.  should i write her back again to be polite / continue to express my interest, or am i really just bugging her (where she's like "oh god; i have to write him back AGAIN...)?  what's the proper etiquette here?
	
		
			
		
		
	
				
			 
  
 
		 
 
		 
 
		 
 
		 
 
		