Use of Credit Cards for online tickets

What exactly is the issue? It's not US cards specifically, but if the bank doesn't support two factor authentication (either by approving a transaction using a notification from her banking app or entering a code from an automatic text message from the bank) that may be the issue. Depending on the bank, she may be able.to get them to activate 2FA.

Alternatively she can open a debit account with a fintech provider like Revolut or Wise, which do use 2FA.

Did she notify her credit card issuer that she would be traveling abroad? She probably needs to put a “travel alert” on her credit card account to let the credit card company know that she is traveling and to what county/countries.

I think the problem is it’s probably screaming fraud because it’s a US based credit card being processed from a computer in another country. I think the only thing you can really do is call the credit card issuer and ask them what you need to do

Travel alerts are great for physical use, but the virtual online use is probably not covered as much. .

She is probably running up against a common method of authentication used in Europe that is like 2 factor ID. Basically, for online purchases, many Europeans then get a text with a code for you to input as validation. Most US cards have not activated this feature, Mastercard calls theirs Secure ID, Visa's is 3-D Secure. What may be happening is that the vendors system is trying to authenticate the transaction, getting no response, and then cancelling the transaction.

You can look into her card, see if it is a feature that can be activated, can't say that it is a high probability, but worth asking. Sometimes, for foreign transactions, websites will use a separate portal for transactions, and another for locals, it may even be automatic based on IP address, which hers would show as local, so looking a little deeper on the sites she wishes to use may help.

Is the card your daughter is using also used by someone in the U.S.? If so, that might be the problem. Chase sees a U.S. card being used in the U.S. and in Prague and that's sending up red flags.

Has she considered just not using the Chase card and signing up for something like Wise while she's here. Just keep that card topped up with whatever is needed.