Freeze has a certain resistance check. For lvl 5 they may have max 30 spirit res IIRC. And to be honest Josifina has 75. Maybe you should try and give her a piece of her own medicine. Blind her! Or curse her a few times and then freeze her.
I also find it a bit weerd that even the lowest orc dont freeze anymore. It is possible that there res has increased. BTW witch orc are you referring to? The ones near the cave of Josefina? They are a bit stronger the the usual orcs. I think there res was higher there.
If you want more tips on killing her follow theselinks
http://lariancom.siteprotect.net/ub...ew=&sb=5&o=&vc=1http://lariancom.siteprotect.net/ub...ew=&sb=5&o=&vc=1http://lariancom.siteprotect.net/ub...e=&view=&sb=5&o=http://lariancom.siteprotect.net/ub...e=&view=&sb=5&o=