The brief was to create a direct mail package that educated potential donors about Dress for Success's work and convince them to support the cause.
helps disadvantaged women achieve economic independence.
Davies, who is a senior designer at London design firm The Set Up, won $500 (£284).
She also had help from designers Dan Frau and Joseph Nation.
Katarina Skoberne, co-founder of OpenAd.net, said: "We are thrilled to have collaborated with Dress for Success -- empowering women in business is a cause close to our hearts at OpenAd.
"Not only was this pitch a great opportunity for the OpenAd creatives to showcase what they do best, but the submissions were a unique view into the way that this great cause resonates with audiences far beyond Dress for Success' traditional reach."
launched in 2005 and allows advertisers to post briefs to attract responses from creatives, and creatives to post ideas that advertisers can buy.