If you mean herbal remedies, then yes, she makes potions.

[Light knows she made him drink a lot of them, whenever he lied and whenever he got sick. He makes a face at the thought of the taste of those, what little he remembered of them anyway, and then shrugs.]

Nynaeve was able to tell because she can use saidar. Is the old woman a mage? [That's one of the names Matthew had said magic users go by in his world. Worth a try.]