cause of fever cannot be detected

[Tehseen]

my mother had a by-pass 16 years ago during which she was given blood. for a long time she has been complaining of  fatigue. she  has lost appetite as well  as weight.2 weeks  ago   she underwent a histarectemy that went off  well  though her heart is  not   too strong & she is diabetic. due to  her age (66 yrs)  the  doc kept  her  for a day longer. that night  she developed fever .  then it was  noted  that  she had a low platelet count.the concerned  doctors   were  called  & we were informed  that she had contacted  hep c 16 years ago. the  next day she was  passing blood in her stool. her stomach was bloated.hep c test was negative. by evening she was better . no more blood was being passed, no fever bloating had decreased.
the next morning she was vomiting blood . the doc has sealed up 5 portal veins.again she was given blood. but for the last 5 days she is having fever (102) . all test have been done but she shows no signs of infection. malaria test is negative. inspite of this she is on malarial drugs.stomach is bloated again.this evening they took out fluid from her abdomen which is clear but it has been sent for testing.doctors are not able to pinpoint the reason of fever even though they are giving her broad spectrum anti biotics.
1)can there be any cause of fever which the doctors have   overlooked?
2)will this fluid in her stomach form repeatedly?
3)can she bleed again?
4)is there any precaution that she should take to prevent     futher bleeding?