My parents took my daughter to Venice at the beginning of the year and got me to write a letter to "authorise her travel" which I thought was completely pointless as it wasn't an official document as such and hence could have easily been forged.
Of course no-one asked them any questions and the transition through the borders were uneventful, as you would expect within the EU (freedom if movement of people and all that).
So I wouldn't worry - your daughter will vouch for you
