Both Uses

heathen
in
A Great and Terrible Beauty
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Oh, my dear, yes, caught in the woods with a heathen.†
Chpt 11 *

heathen = someone who is not civilized or not moral OR an offensive term for a person who does not believe in a preferred religion
For a heathen, that is.†
Chpt 24

Definitions:

(1) (heathen)
an often offensive (sometimes humorous) word for someone seen as uncivilized or immoral, especially because she does not share the speaker’s religion or comes from a culture unfamiliar with it

This word is usually judgmental or insulting, so today it is used mostly in joking contexts or when describing older attitudes.
(2) (meaning too rare to warrant focus)
More rarely, heathen can refer to a person who lacks culture or good taste.