You're lucky she still found some, I thought these were sold out months ago, unless USPS re-printed more due to the demand (good sign). Note that these are forever stamps as well.
They must have printed more - I was able to order some from the USPS website just a couple of weeks back with no problem. People must be digging them because I've gotten a few bits of mail with these stamps used. They're fantastic.
Yeah, I think it's been at least a month or two since I bought mine at the post office. I was going to buy a couple books and just use them for the rest of my lifetime, but I thought it was a bit too obsessive. lol