We love us some Cousin Drusilla. She's tough, smart, and independent. The first sight of her in the novel is a little bit shocking for the times. You might not feel like it's that scandalous, but Dru's style caused as many gasps as Miley's VMA performance:
Then we all heard the horse at once; we just had time to look when Bobolink came up the road..., with Cousin Drusilla riding astride like a man and sitting straight and light as a willow branch in the wind. They said she was the best woman rider in the country. (3.2.12)
This might be the first time we see Drusilla compared to a man, but it certainly won't be the last. She's a tomboy to a T. One of the reasons she's branded as unladylike is her connection with nature: she likes to ride horses and work in the fields. And Bayard's comparing her to a willow branch gives us a taste of this connection between Cousin Drusilla and Mother Nature.
Dru being the best woman rider is saying something in a time when horses were the most common mode of transportation aside from walking. This skill comes in handy for more than just impressing her cousins, too; she becomes quite a formidable Confederate soldier.
Of course, being a Confederate soldier wasn't exactly an acceptable profession for women; Drusilla has to run away from home in order to do so, and she pays dearly for the time she spends with a troop of men.
She makes it clear, though, that she didn't fight alongside John because of love or anything as humdrum as that; she's all about breaking the rules and finding a new way to define herself that goes way beyond being ladylike. It's like she tells Bayard:
"Living used to be dull, you see. Stupid. You lived in the same house your father was born in and... then you grew up and you fell in love with your acceptable young man and in time you would marry him... and then you settled down forever more while your husband got children on your body for you to feed and bathe and dress until they grew up too... But now you can see for yourself how it is, it's fine now." (3.2.48)
Drusilla might be being facetious with her "it's fine now" (it is a war, after all), and later on she makes it clear that she's very sad that her fiancé was killed and wants nothing more than to "hurt Yankees" to pay them back for her loss. But even if she is being a little sarcastic, there is something to her appeal for freedom and the way the new frontier attracts her.
So you can't help but feel terrible when Drusilla's mother finally tracks her down and makes her put on a dress. It's like that wild, free spirit has finally been tamed: "But she was beaten, like as soon as she let them put the dress on her she was whipped; like in the dress she could neither fight back nor run away" (6.2.21). After she's been forced into a skirt, Drusilla starts to fit into the mold that has been cast for her.
However, Drusilla doesn't suddenly go all goo-goo for gladiolas just because she's been forced to be a lady. She still rebels. She kisses Bayard (technically her stepson) for one thing. However, when John is murdered she doesn't take matters into her own hands, like she did when her first fiancé was killed; she wants Bayard to do it, and rejects him bitterly when she realizes he doesn't share her bloodlust.