What Cause Rashes All Over The Body After Taking Ativan?

my mother had her first chemotherapy session for CLL and within 6 days became nausious and was given a good dose of ativan. Upon leaving the clinic was totally out of it, within 3 hours had a rash all over her body, throat and face were so swollen, when she tried to speak only a squeak would come out. Was admitted to the hospital that evening and was continually given ativan. Within a couple days she had a breathing tube put in because doctors were afraid her throat would close up. She never gained consciousness and passed away 6 days after that. After reading up on this drug and the serious side effects, I kept asking the doctors and was just blown off. I was told it was just a side effect of the chemo.