It sounds like your daughter might be printing it out at a resolution of 72, the same resolution it probably arrived in if you sent a jpg. This would account for the huge physically different print size (though the quality of her print must have been quite bad). You havenít told us an important piece of information however...what resolution did you scan the wallet size photo at?
But in any case, assuming she has an image editing program (like Photoshop Elements or one of the others) if she just assigns the same resolution that you scanned it in at the print size on her end will be the same size as the original. If she doesnít have an image editor she could insert it into a word processing program like Word Perfect or Word and use that programís tools to scale (resize) it down to whatever smaller size she wants and then print it out.