Guren was a powerful, I mean crystal release? She was arguably stronger than the Sound Four. WHy didn't Kabuto bring her back to life when he was the one that killed her? He had her DNA.
Guren was never killed (Though unable to perform any hand signs (with her hands busy holding back Rinji's arms), Guren still managed to use the Crystal Release and crystallized herself and Rinji. The two fell into the water below. Gozu later saves her.), in fact, she is even seen later in Naruto Shippuuden:
After the final battle between Naruto and Sasuke, Guren, Yūkimaru, and Gozu can be seen in the crowd at the entrance to Konohagakure.