Swollen hands, weak hands and arms

My daughter is almost 4 weeks postpartum (c-section) and is experiencing some weird symptoms. About a week ago she started complaining that her index finger on her left hand felt like it had been jammed - although she had done nothing to injure it. By the next day her hand was swollen and sore.... By a few days later her muscle stiffness had moved up her left arm and into her shoulder and neck and by the next day had pretty much lost use of her left arm and hand. She had no grip and could only move it a little. She looked like she had had a stroke (but only in the left arm). I had to give her the baby to feed (propped on a pillow) and then take him back to burp and change when she was done. Went to the ER and they  gave her a prescription for 5 days of steroids. The next morning her arms were better (but not good). By early evening the right arm was very weak and the hand had no grip. Over the next few days it seemed to come and go but never getting good.  By the 4 day of the steroids she had limited use of her hands, could grip things but not great. She also couldn't (without a significant amount of effort) lift her arms to shoulder height. I spoke with her this morning and she said her arms are "useless."