n. A Muslim woman who dresses fashionably but modestly, in accordance with her religious beliefs; a person who designs fashionable clothing for Muslim women.
Welcome to the world inhabited by the "Hijabistas", a trendy set of up-and-coming Muslim fashion designers who are doing their bit to forge an indigenous British Islamic identity.
—Jerome Taylor, “Beautiful and Islamic: the new look on the catwalk,” The Independent, July 02, 2010
As the trend of wearing hijab spreads, so, too, have hijab fashions. Women from New Jersey to Jakarta are trying new ways of wearing wraps taught on YouTube or showcased on runways.

Whatever the look, hijabistas share one style principle: This is not their mother’s head scarf — conservative, plain, a little too formless.
—Carol Huang, “The Muslim veil: modesty has its own style,” The Christian Science Monitor, December 12, 2009
2009 (earliest)
—“Hijabista Style Steal: Mauve on Over Muna Abu Sulayman,” Ilovehishma, March 11, 2009
A person calling herself Hijabista posts frequently to various blogs, and the earliest of these posts I could find was a comment from August 13, 2008.

There's also the private blog that Google dates to June 28, 2008, but I can't confirm this.