Wait, why not make her a character who puts up stalls inside the middle of the dungeons (rest stops or whatnot) and makes sure to stock up on necessities adventurers might have missed. Herself being self-sufficient (she's had lots of experience), or has a partner who has the same hobby.

She has very competitive prices--just a small markup for her troubles. And has become an urban legend amongst adventurers as "granny mart". Some rely on her foot cream, others for her home-cooked meals, and still others for her effective home-made potions.