corn occasionaly stops eating for 4 months is this normal...

[Nicky]

for about 1 year my cornsnake nicky ate dead mice then out of no where she stopped eating i kept trying to feed her buit she wouldn't take it i even tryed life then 4 months later i was trying to feed her a live mouse and she ate ever since shes been eating only live mice but i want to switch her back to dead mice becuase the live ones occasionally scratch her and i don't want her to get hurt but no she won't take dead or live again??? she hasn't been eating for about a month wuts going on how come she just keep stopping and then starting again? shes in a 35 gal tank with 4 inch thick bedding to burrow in and a large water bowl with 2 hide boxes and plants and in the day its about 80.c and at night 70-75.c. is it something with the set up thta makes her stop eating or could it be something else she dosen;t have mitts could it be an internal infection or is it normal?