It looks your aunt had landed in acute renal failure
Since she is a patient of diabetes
,she would definitely require a renal transplant for the best outcome but the proper approach at the moment would be to go for dialysis.
Let the patient settle first from the trauma of surgey and then renal transplant can be undertaken later on depending upon the situation at that time.
Consultation and advise from the nephrologist
would be the best thing to do at the moment as he can assess the patient properly.