Sheen joins from the Emap young women's title, where she was deputy editor and helped to relaunch the title.
A revival in fortunes for women's glossy B, which suffered a 14.3% fall in circulation to 165,431 when its last ABC figure was published in June, is one of Hachette's priorities.
Last week, it appointed Rita Lewis as publishing director of Red and B, with the task of developing both titles.
Sheen, who has also worked on Closer as specials and lifestyle editor and J-17 as acting editor, plans to create more of a buzz around the title.
She said: "B is a title that has done well over the years but is not talked about nearly enough. I plan to change that with a new, refreshed vision for the magazine, making it a major player and a major rival in the women’s magazine market."
Sheen succeeds Gina Johnson, who stepped down as editor in October 2003 to work on special projects at Hachette.
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