Any of the moments when we see that Scarlett truly does care for her children.
Rhett comforting Scarlett and promising he will help her get home to Tara, the evening of the first burning of Atlanta.
Scarlett's reaction when Melanie miscarries and they know she's not going to make it. It's both heartwarming and heartbreaking.
Likewise when Scarlett and Ashley are caught embracing and Scarlett's biggest fear is what Melanie will think.
The talk Rhett and Wade have on the day Bonnie is born.
When Pork gets shot trying to steal food for everyone at Tara Scarlett tells him how grateful she is to him and promises to buy him a gold watch when she can afford it. When Gerald dies she gives Pork his watch, knowing how much it would mean.
After the rumours that Scarlett and Ashley are having an affair start, Rhett forces Scarlett to attend Ashley's party by herself in a provocative dress. Melanie's reaction to Scarlett's entrance is to walk over, kiss her on the cheek while complimenting her dress, lead her over to Ashley, and tell him to get Scarlett some punch. This also arguably qualifies as a Crowning Moment Of Awesome on her part for making it absolutely clear in her usual calm, polite way that her trust in her husband and sister-in-law will not be broken by gossip.
When Melanie personally thanks Hooker with a Heart of Gold Belle Watling for providing an alibi for Rhett, Ashley and Dr. Wade after the shantytown raid. Though Belle is concerned about what this might do to Melanie's reputation, Melly dismisses such talk and says she's proud to know Belle.
Melanie giving up her wedding ring for the Confederate cause, and a genuinely-touched Rhett redeeming and returning the ring to her.