Did fatima bath before her death so that none washed her body?

I read in ibn al jawzis work talbis iblis that Shiism believes Fatima washed herself before her death so that it would suffice for funeral wash. (Page 177 English translation) Is this narration correct, if its correct how does it take care of any discharges from anus and private part post death? Secondly how does she know shes going to die in few minutes or hours? Doesn't this contradict Shia view of imams only being inheritors of knowledge?