So far it's interesting. You're very heavy on the exclamation points, though. (And Sgt. Morrisson's whole first letter to Zacky was full of exclamation points.)
There's not been much character development, and you skipped a whole year so we didn't get to see how they bonded. We know nothing about this Sgt and what would make Zacky like her enough to ask her to move in with him (when he still has never met her before).
Her reaction to finding out who he is may or may not be a little unrealistic. I would be a heck of a lot more shocked, or possibly angry with him that he kept his identity from me for a year. And how exactly did she bond so much with him, if he has never sent her a picture of himself or told her what his job is?
It's a great idea, I just think you need more detail, more character development, and to lay off the exclamation points.