Isn't Barb a genius? Wow!

Anyway, I would just add: put the remedy in a water bottle and tell the patient to shake the bottle before each use. This will prevent antidoting of the dose that may be still working
and Hahnemann says in the Organon that the vital force rebels at the same dose being repeated over and over again, so he suggests dosing in water and
"dynamizing" as he calls it, meaning to succuss before each dose.

OK, having said that, at some point Arnica may stop doing the job because symptoms specific to other remedies may make an appearance, and you'll change your prescription as these things arise.
For example, she may say to you, "I'm being bothered alot by stiffness! It's better after a hot shower." So, you'll give a dose of Rhus tox 30C in water to take as needed and see how that does. Or she might say, "I have numbness and tingling and sharp shooting pains!" So you'll give Hypericum in the same way; and consider that 30C may not be high enough, but it's a place to start. She might say, "These pains are so bad, I can't even move, I feel like I'm locked!" So, now you'd give Bryonia. So, this is a possible scenario; you have to follow what presents itself.
If Arnica isn't working, and she's complaining of symptoms that look like Hypericum, etc., then give that remedy, and you may find that the Arnica symptoms present again. This is a great case, we're anxious to hear what happens!

Snoopy