what does "The stone-cold-sober DD"mean? what does "DD"mean?
Otherwise, tonight’s crowd leaned heavy on beer and wine. She kept her tables happy—casually flirting with guys, complimenting girls on hair or shoes, laughing at jokes, quick conversations with familiar faces. She enjoyed the work, the noise and the hustle. She liked the people-watching, the speculating.

The stone-cold-sober DD from her table of five channeled any desire he might have had for beer into hitting on a nearby table of girls, par-ticularly the milk-skinned redhead. From her reaction, the way the two of them danced, the whispers when the girl group trooped off as a pack for the ladies’, Abra figured the DD might just get lucky later.

Question

what does "The stone-cold-sober DD"mean? what does "DD"mean?
Otherwise, tonight’s crowd leaned heavy on beer and wine. She kept her tables happy—casually flirting with guys, complimenting girls on hair or shoes, laughing at jokes, quick conversations with familiar faces. She enjoyed the work, the noise and the hustle. She liked the people-watching, the speculating.

The stone-cold-sober DD from her table of five channeled any desire he might have had for beer into hitting on a nearby table of girls, par-ticularly the milk-skinned redhead. From her reaction, the way the two of them danced, the whispers when the girl group trooped off as a pack for the ladies’, Abra figured the DD might just get lucky later.

Answer

DD means designated driver.  The person designated to drive therefore they are staying sober and not drinking.

Answer

DD is a Designated Driver. 
Someone who is appointed to stay sober and not drink alcohol when you go out to the bar or club so everyone has a safe ride home.

Answer

It's vague what the DD means in this context. If the "DD" is a woman, then I would understand "DD" to mean "double D" which is a large bra size. So just like "the milk-skinned redhead" is talking about a pale, woman with red hair, "the stone-cold-sober DD" is possibly talking about a woman with large breasts who is not drunk.

But here its referring to the "DD" as 'he' so unless its a cross dressing male, I couldn't guess!

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