Would 5 doses of Valium and 5 doses of Dilaudid within an hour cause the death of my mom?

It may or may not have caused her death. It sounds like your mother had Ascites. This is the end result of liver failure due cirrhosis and a person in this condition is going to die. If end-stage cirrhosis causing liver failure was a big factor then it may not have mattered as to whether the health care professionals gave her both Valium and Dilaudid. However these meds would've allowed her to pass on pain free and in peace. Otherwise wihtout them, she may have died a very agonizing and painful passing

Hi, IamBuda,
That combination could actually cause central nervous system depression including respiratory distress that can be severe.
I don't mean to upset you but you need a copy of the Death Certificate which will show the cause of death and also ask for a copy of the toxicology report. Question the primary attending physician. Most hospitals have a patient department that can handle questions like yours.
I'm so very sorry for your loss.
Best regards, Wildcat