Ugh same! Have the same issue with the first sister and after many defeats i cant interact with the corpse. The higher 2 sisters I can interact with just fine. Ugh!!
There are 3 sisters that are seers. Each carry a sword to use to help unlock thors hammer. The first sister (Gonril) its glitched and wont let me interact with it to fight her! The other 2 sisters I can. It's just her.