I have a question about etiquette, and I thought it might be a good idea to have a thread devoted to the genre. I can't be the only one who needs a little "Miss Manners" advice now and then!

To start things off, here's mine:
A friend of the family sent me a set of 8 notecards. She attached a note that said that she thought of me when she saw them and wanted me to have them. When I write my thank you note to her, is it ok for me to use one of the notecards? I'd love to do that, but I didn't want her to think, "I didn't mean for you to write ME on them - now you've wasted one!" But, I really do love them and can't think of a more perfect thank you note than on the cards themselves. Ok? Not ok?