What to say in the card

Congratulate her on the birth of her child and becoming a mom. Skip the thank you's. There are lots of reasons I say that, the biggest being I can't think of a single first mom who wants to be thanked for placing their baby. We don't do it to get thanked, we do it to give our little one a life we feel we can't provide. I would say honor her as a mom during the short time she gets that honor. It may be hard for you, but I think in the long run you will be glad you did.