It's very simple. You produce evidence or proof that two things are related.

Living in the same house as a medical doctor does not make me a medical doctor, nor does it make modern medicine responsible for my actions.

The argument isn't that she was a homeopathic "doctor". The argument is that she was influenced by the ideas behind homeopathy, and because of that influence the "treatment" she administered made sense to her. Her logical reasoning had been clouded by her belief (essentially a religious belief) in homeopathy. This is akin to religious groups who refuse to allow medical treatment for their children, who subsequently die.