Perhaps request some samples, telling her you have concerns re: tyrocine effects (as MrsD points out). If samples are not available, ask about her return policy should unpleasant side effects occur.

Otherwise, maybe invest in a supply and see how you feel. If they don't seem to be helping, you don't need to continue purchasing.

I recently had a similar decision. The Naturopath who works at my local health goods store recently told me she had a herb I could try (apologies, i dont remember the name of 'miracle' herb). However, this herb was going to cost me around $200 per month. I almost fainted! I politely thanked her, but explained that my finances couldn't stretch that far without a guarantee these herbs would cure me. She claimed they would in a few months. It was then I lost faith in her. If a herb could cure neuropathy then we wouldn't all be here living this hell!