She needs to go to Paypal.com and make sure she has an account. Then she needs to click on 'Edit Profile', then 'Credit/Debit' cards under Financial (middle column). Then click on the orange 'Add a Card' button if it doesnt show up in the list of cards.

To confirm the card, Paypal will charge two small amounts and she'll have to enter those amounts into a page on paypal once this happens to verify that the card is hers.