Ruptured AVM

I am a student in my last semester of school. I am working on my preceptorship in a local SICU, and had an extremely upsetting case yesterday. A young lady came in a few nights ago after being found unresponsive. She was intubated by paramedics and brought to the ER where it was found she had a massive hemmorhage, likely due to a ruptured AVM. On her CT you cannot even make out the ventricles because her head is so full of blood. Her pupils are 9mm in size, fixed and nonresponsive. SHe is unresponsive to painful stimuli. GCS of 3. She is in full pulmonary edema, as well as renal failure. Her vent tubing is being changed every few hours because it continues to fill with blood. She is on full vent support. She is maxed out on Levo, Vasopressin, and Dopamine. She had a flat EEG, and failed the ear canal ice water test, corneal reflex test, and apnea test. She has been declared brain dead. However, the family continues to hold out false hope that after three days she will magically recover and walk out of the hospital. Today is day three with no change. The family is still insistant that there will be a miraculous change. My question is, am i being realistic in knowing that there is no coming back from this. Am i being too negative because i think this is totally irrational and cruel to the patient, to continue to hold out this hope? I try to put myself into this family's position and think what i would do if this is my family member, but i cant see holding out such hope for long. What do you all think is the appropriate time frame in a case like this, and am i destined to be a bad ICU nurse because i just cant bring myself to be so positive about such a patient? This really hits hard on me, because the patient is my age, and was so young, healthy and full of like just three days ago. Any advice on dealing with this would be great!!!