All 3 Uses of

discreet
in
Gone with the Wind

At the party tonight, women would gather in corners and whisper discreetly and with malicious pleasure.†
Chpt 5.53 *

discreetly = in a manner that is unlikely to attract attention or cause embarrassment

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

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.