
Thats a really sweet and thoughtful idea :D
My (teenage..bovvered???) sister stayed with us a couple of weeks ago and much as I love her I gladly waved goodbye to her and her hormones at the end of the week....only to find after she'd gone a very touching thank you letter slipped onto my pillow when I went to bed *sob* *guilt trip*
(thank you's especially soo personal..worth their weight in gold :D)
I'd say get your frame work for the poem but save it til the end of the trip to complete,so you speak from experience that way you'll be able to put in some personal lines that show you remembered or noticed the little things she did to make you feel at home and you appreciated her hospitality.
Have a great time :D