Friends who haven't contacted for five years are now in arrears with their credit cards. The bank calls me now and sends me a text message asking me to inform her.

This situation should be that when she applied for a credit card, she filled in your mobile phone number as an emergency contact.

If you want to be friends, you can help me get in touch. If you can't get in touch, just reply to the bank directly.

This matter has nothing to do with you, so don't worry about anything.

She hasn't paid back the money yet, and eventually the bank will look for her, and certainly won't let you pay back the money. It's just that you wrote your contact information when you applied for a credit card, and the bank tried to ask you. You are just an emergency contact, not a guarantor, so really don't worry.