All 3 Uses

discreet
in
Gone with the Wind
(Auto-generated)

Then, after a discreet pause which gave Gerald's splutterings time to die away, she knocked on the door and handed the dress to her mother.†
Chpt 1.4
A discreet knock sounded at the door.†
Chpt 2.10
At the party tonight, women would gather in corners and whisper discreetly and with malicious pleasure.†
Chpt 5.53 *

Definitions:

(1) (discreet as in: discreet--not showy or gossipy)
trustworthy with secrets or subtle (not attracting attention)

This sense of discreet sometimes indicates that something is small (so as not to attract attention) as in "discreet earrings."
(2) (discreet as in: discreet--not foolish)
sensible and careful; possibly having good manners

This sense of discreet is more commonly seen in classic literature than in modern writing. There is may also refer to having the judgment to exercise good manners.
(3) (meaning too rare to warrant focus)