Like I said earlier, this wasn't about hair not getting braided.........or her not cooking.
There's just something wrong with dude mentally that caused him to react the way that he did.
You're asking where does it stop, right?
Well, with mental illness..........there is no one-size-fits-all manual or limit to what they're capable of.
There's mentally ill people who don't commit acts of violence..........and there's mentally ill people who do.
In which case, there's nothing anyone could've done either way to prevent him from killing those people.
If she braided his hair, he could've snapped because she didn't braid it right.
If she cooked for him, he could've snapped because he didn't like the way she cooked it.
Basically, when dealing with mental illness..........there's no telling how a mentally ill person is going to react to anything unless you go by their past history.
Even then, the way they reacted in the past isn't necessarily indicative of how they might react in the future.