I currently am penpals with a girl who I met when I studied abroad in Spain. On average, we'll probably exchange 5-6 letters a year (12 in total), and I really would like to know a good away to go about seducing her.

I don't think I am in the friends zone, but then again, I am not sure as to how to begin the seduction, especially in something as antiquated as a letter.

Any advice?