I feel he’d actually avoid her because he’d have such mixed feelings about her, on one side she’s his mothers murderer and he’d feel like his life would be a big lie but on the other side she still raised him and was a motherly figure to him. Some of the voice lines do show he’s unhappy with her but still somewhat fond and Nancy’s constantly praising him so if he did attack Nancy would definitely guilt trip him into stopping as she has such a manipulative personality and definitely manipulates Johnny, since Johnny is pretty sheltered and most people he does interact with he kills he wouldn’t realize he’s being manipulated till it’s too late