I would discuss it with her privately if you haven't already. If she is a good friend and she means a lot to you, then I see no reason why the two of you can't discuss it calmly and rationally. Perhaps you can help her see things in a different way.
If you've already discussed it with her, and you believe she is simply putting her own desires above her child's needs, then you have to weigh whether her friendship means more to you than your desire to see her child receive help. It's a tough decision. I don't envy you.
If you've already discussed it with her, and you believe she is simply putting her own desires above her child's needs, then you have to weigh whether her friendship means more to you than your desire to see her child receive help. It's a tough decision. I don't envy you.