Alternative ways of paying for online purchases?

My girlfriend wants to get a thing, but her mom said her dad can’t know she has it or else he will go completely crazy on her. Now, some of the items she needs for said thing have to come from the internet. She can’t use her credit card cause her dad will see everything she buys. My mom wont let me help her out cause she doesn’t like my girlfriend to much (but that’s another story).

I had heard that you can purchase a a Visa Giftcard and use that to pay for things you buy online. Is there any legitimacy to this?