If it is a sharp pain i would not wait and IŽd take a tablespoon of Epsom Salt and would go for another flush as soon as possible.
I know that right after a flush we need a break,and some time to get our energy flowing again, but when in pain IŽd not wait.
Maybe the Epsom Salt will do the trick and your friend will feel better, but if pain persists flushing will do her good. The worst that may happen is that yr friend will lose some weight by doing two consecutive flushes.