Every time Claire was overpowered on the battlefield, she pressed on her ability to the next level. This scene was happened after Flora gets killed, and Claire must defended Milia in all cost from being slaughtered by Rigardo. So she was transformed one part of a body at a time, and nearly became full kakuseisha.
One of my wishes is that somebody will make Claymore movie. Since Claymores setting was medieval Europe, it must be done by western people. Just cast smart actresses for them, and put Weta or ILM on CGI, then we will have great entertainment. Peter Jackson, are you up for the challenge?
Claymore and all of its elements are copyrighted properties of Norihiro Yagi and/or their respective owners.