Not everyone lives in dresses so the idea of having to buy one for a holiday work party can be stressful, boring, fun or all of the above.
When dressing for a work event you need to keep in mind that these people need to take you seriously the next Monday in the office. No deep Vee for them to picture when they see you back in your suit. No ass peaking out of a short hemline for them to imagine when watching you walk away. Keep it sexy without being sexual and fashionable without being deemed ridiculous.
A safe bet is to wear black, but don't settle for just anything. This draped Alexander Wang dress with the beige lace racer-back is sexy, interesting and still completely appropriate. The ruching and draping ensures this isn't a "tight" dress as well hides any bumps and bits we don't want to show. Still the closeness to the body inspires some respect for the woman's body.
Granted the open vee at the hem could have them drooling so add some opaque tights to the ensemble to make the look more work appropriate. Top it off with some party pumps that will elongate your look and give you the power player look.
Now, all this black seems a bit dreary so the jewelry needs to have some color and punch. This long gold cuff is fabulous and the blue in the earrings will give you the creativity this dark image needs.