wbr

My sister finished the last of her 10 WBR a week ago Thursday. She was feeling surprisingly well...much less fatigue then we had anticipated. Two days ago, almost a week after the last treatment, she feels incrediably weak. She can barely walk up a short flight of stairs. She said that it feels as though her "legs are giving out". For those who have had WBR, did symptims start after the treatment? How long did it last? Did you have similiar symptoms as those I've described?
I want to be able to call her and reasure her that this is normal, (if there is a normal when it comes to cancer treatment!). Thanks in advance,
Celina