Battle Girls: Time Paradox

Extended title: Battle Girls: Time Paradox 2011-04-04 to 2011-06-27
 * Sengoku Otome - Momoiro Paradox (Japanese)
 * 戦国乙女～桃色パラドックス～ (Japanese)

Plot
Modern-day middle school girl Hideyoshi is mysteriously hurled into a world resembling the warring states period of Japanese history, only this time it's inhabited only by women. This world's Oda Nobunaga is gathering the legendary Crimson Armor so she can rule the world, and for some reason needs Hideyoshi's help to do it.

Other Sources
http://www.animenewsnetwork.com/encyclopedia/anime.php?id=12506