Originally Posted by
marklyon
A passport card is a passport and, to my knowledge, you can't get the card without a passport.
That's not correct. In the words of the state department:
TRAVEL DOCUMENTS FOR U.S. CITIZENS
Apply for one or both, it’s your choice.
If all you need is the card, you can save some money by just applying for that without having to get a passport book.
They also state
US Passports, either in book or card format.....
Which to me implies they treat both of them the same.
But I am not an immigration lawyer and would suggest checking with one for the full ramifications of you getting either a passport or a card for her.