so, what, in your opinion would be the #1 'Mcdougall thing' to do to lower high blood pressure?
Adopt the McDougall Plan (Regular) completely, consistently, and without exception.
I'd love to help her but [...]
Does she want help? If not, then I would suggest that there is nothing you can do. Influence means giving people information they
want -- for the purpose of reaching goals they
have set for themselves
She's the type of person that will probably rather pop a pill than to eat right.
If that is actually the case, then I suspect you can't do anything. I have been in that situation, with friends who have terrible habits. When they tell me about their worsening symptoms, all I can say is to state the facts as I know them: "Yes, I am sure your blood pressure is high. I can see three causes: drinking, smoking, and a high fat diet. There is a solution. You might look at the McDougall Program, for example."
If she rejects your comments out of hand, then I would stop making any further attempt. If she is eager for a solution (other than pills and surgery), then you can answer her questions, one by one. My experience is that sugar-coating the truth never works. I bluntly state that only a wholesale change in lifestyle offers hope.
I wish I could offer a bright picture, but I don't think there is one.