perspective guest is claiming that the rental application says nonrefundable

[Anton42]

Although my hosting page says full-refund up to 5 days, the guest is hesitant to book because she claims the application window

for payment claims her payment is non-refundable. she says this info comes up right before she is about to enter her credit card information.

[Paul154]

My  reply would be "oh that's interesting. I didn't know"

Meaning "Not my problem. It's between the guest and Airbnb"

While it may be true NEVER believe anything a guest tells you about Airbnb.

They are often confused, or tend to drama. 

Best to say, 

"That is between you and Airbnb, I have little control over that"

[Fred13]

IF your ~intent~ is to honor a "Up to 5-days" full refund, then whatever Airbnb says or does is secondary, because there are ways for you to DO honor your own personal policy, which Airbnb makes easy to use.