Nanashi no Tensei: Queen's Blade

Nanashi Tadano [translates as "Typical No-Name"], an overworked office lady who died from overwork, is reincarnated as the unremarkable Nanashi in a world that looks exactly like her favorite anime, Queen's Blade Legend. It's an alternate world where sexy female warriors known as ‘Beautiful Fighters’ battle it out with inhuman skills known as ‘divine seals’.
Nanashi accidentally frees a legendary demon and becomes a beautiful fighter with the most overpowered skill, the 'Shapeshifting Right Arm'.
She'd normally use her power to fight in this world, but...
"I'm not interested in duels. I'm satisfied as long as I can watch my favourite characters fight up close."
In this other world, where dueling is based on the harsh rule that ‘winners take all’, Nanashi's otherworldly life begins as she hides her mighty power in order to see her favorite beautiful fighters in action up close and personal!

(Source: Firecross)