"The Alexa App must be logged onto an Amazon account." The typical Amazon Account will have Payment Methods on the account. Anyone logged into YOUR account can access your payment information.
OPTION 1: Your Amazon Account
If your Loved one is in their own home and your comfortable with them using your account you can log them in as you.
OPTION 2: Your Loved Ones Amazon Account
If your Loved one is in an Assisted Living Home, it is recommended they are using / provided an Amazon Account in their name with NO payment methods set up.
Pro:
Other people can converse with your loved one without you (your account) being involved.
Con:
A unique DEVICE is needed for the loved one's Alexa App install. If they have their own smartphone this is perfect. (even if the phone is no longer active, it can be logged on to any wifi to do configurations)
Note:
Often people have an old phone or tablet they can resurrect for this purpose.
The following is NOT needed if you are adding your loved on to your own account. (OPTION 1 Above)
Configuring You Loved One's Alexa to have YOU as a contact and allow YOU to drop in on them.