I've ordered address labels for my kids and gifts from a reputable company called current. They are reasonable, too. I just checked and they do have some personalized stationery but it's somewhat limited. Here's the website:
You could also go to online photo stores such as snapfish.com and make thank you cards from photos of your daughter. You could capture a part of her bday.... maybe eating cake or opening gifts and create a card from that. I've used this website for making cards. To cut costs, you could just personalize a photo. Walmart, Target, Walgreens, etc... all do this service, too.