Voldaren Pariah transforms on it's own

Hello,
I'm having trouble with Voldaren Pariah transforming whenever she wants causing my opponent to sacrifice 3 creatures and without me sacrificing any. The transformation goes onto the stack in excess of 20 times. It is completely random and sometimes doesn't happen. Screenshot attached.
Best wishes,
Adam
I'm having trouble with Voldaren Pariah transforming whenever she wants causing my opponent to sacrifice 3 creatures and without me sacrificing any. The transformation goes onto the stack in excess of 20 times. It is completely random and sometimes doesn't happen. Screenshot attached.
Best wishes,
Adam