I completely agree, I thought it was one of the most baffling narrative decisions I’ve ever seen.

Cult of Chucky opened the door for something fresh with Charles finally back in a human body, ready to wreak havoc with Tiffany. I was expecting the TV series to do something creative with that concept, with Nica eventually regaining control of her body. But instead, Chucky and Tiffany just end up wanting to kill each other once again, meanwhile Nica (who as you say has already lived a depressing life) gets her limbs amputated. In my opinion, the potential was completely wasted and the choices Don Mancini made were so out there in some instances that it actually felt like fan-fiction to me.