Should someone say thankyou when recieving a postcard from a friend?

I sent a postcard to a dear friend of mine and a seperate one to her child while on vacation. After i'd been home a couple of weeks she hadn't said anything so I ask her if she got them, and she said Yes, but didn't even bother to say thankyou.. It really hurt my feelings, and i was wondering am i just being too uptight, or should she have said thankyou or something?