I'm trying to locate a poem that I read several years ago.  I believe
it was titled "Daughter In Law" and the first line went something like
-
"There are no words with which to thank you for my son's wife - 
Another line had the words "Part woman and part young girl"

I haven't been able to find your poem, but while searching I came
across a different poem that you might enjoy:

To Our Daughter-in-Life

Though you shall be known
as our daughter-in-law
on the day
you become our son's wife...
to us, you shall forever be known
as our daughter-in-life.
For the love that you
have shown for our son
raises you high above
and places you within the realm
of true familial love.
So it is with grateful hearts
we welcome you into our clan
and thank you for the love you bring
to our little boy... grown to man.

Elegant Accessories by Nancy
http://www.elegantacc.com/items/moondrms.html