Colonel Violet is a minor antagonist in the Red Ribbon Army arc. The aforementioned army's only (known) female officer, she is considered by her superiors to be loyal, diligent, and a model soldier. However, she is primarily in it for the money, and is willing to betray her comrades and employers if it suits her goals.
In FUNimation's dub of Dragon Ball, she is voiced by Kasey Buckley. In the Blue Water dub of the same series, she is voiced by Jennifer Bain.
Both actresses are pretty close in terms of performance, but I think Jennifer sells it a little better, most notably when she reveals her duplicitous side. Kasey is just a bit too monotone in that regard.