The chief merchandising officer of Foothill Ranch-based Wet Seal Inc.’s namesake division for teen girls has resigned.

Wet Seal has 473 Wet Seal stores for teens and 81 Arden B stores for young women, and has more than $600 million in annual revenue.

Harriet Sustarsic, who joined the company last November under former Chief Executive Susan McGalla, will stay with Wet Seal until Oct. 19.

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Sustarsic’s resignation follows the company’s announcement that four board directors, including Chair Hal Kahn, will resign and be replaced by four directors nominated by major shareholder Clinton Group Inc. of New York.

The board makeover is seen as bringing Wet Seal closer to a potential sale, which Clinton Group had earlier urged the company’s board to consider.

Sustarsic leaves to become senior vice president and general merchandise manager of the premium denim brand True Religion Apparel Inc. in Los Angeles

Kim Bajrech and Debbie Shinn will now head up merchandising for Wet Seal. The two had served in that role together for a two-year interim period prior to Sustaric’s hire by McGalla in November 2011.

“As partners in this capacity previously for two years, Kim and Debbie led this team under our fast fashion merchandising model,” said Wet Seal President and Chief Operating Officer Ken Seipel in a statement. “During that prior tenure, comparable store sales grew in nine out of ten months from November 2010 through August 2011. Given this proven success, we have complete confidence in their ability to drive the return to our previous fast-fashion merchandising strategy at Wet Seal.”

Wet Seal believes its switch to fast-fashion will help push it past a prolonged sales slump that has so far brought same-store sales declines every month this year.