[@Kingfisher] I imagine the character to be a kind of gypsy, fortune teller-styled witch. She's middle aged, and appears a bit capricious, disoriented, and chaotic to others. However, she herself is perfectly calm and organized in that disorder, which would enhance that superstition.

Maybe she has some kind of trade that keeps her relevant to the outside world and the gangs/individuals of the city. You mentioned charms to reinforce weapons and containers, so maybe she'd be into that. And, also, maybe she'd possess some kind of formula that spikes the potency of Fairy Dust, or prevents coma in the event of overdosing.

However, I doubt she'd get herself involved in whatever is going on in the city without being dragged into by someone else. Is it possible to get an NPC or player to seek her out? Create some kind of urgency for her to get involved?