After Sheila's last hospital visit she had turned to religion to appease her mother. Her inference on good and evil had been evident.
There was the incident of her throwing pots/pans at Colin when they were married and also putting her hand through plate glass when JB took her to hospital. Punching walls while Freddie was at her apartment in Maida Vale. Left to her own devices and she could have done damage.
Mmm. She said that she'd found region to please her mother. She appeared at peace with it.
You appear to have entirely put your own slant onto her behaviours. You seem to NEED her to be violent. Okay, there were domestic incidents -Colin claims to have started some- hitting the plate glass was, I imagine- out of frustration. She wasn't ill on THOSE occasions. However, when she punched the wall in Freddie's presence, she clearly WAS ill and it wouldn't have mattered whether he'd been there or not.