Animals have parasites and diseases, so do plants, there are even bacteria that cann dissolve oil spills or plastic or what have you - why couldn't there be a disease living off magic - a magic item could be infected, losing power and speading the plague to other equipment it contacts, while a magic user would slowly lose his powers and contaminate all he works with or casts a spell at...
How Jayel became the proprietor of the Wanton Wench is more or less a hand-waved affair by the local officials. The facts known by 'upstanding' folk are that a fresh-faced young girl by the name of Jayel came into Gatewatch, disappeared, and reappeared the aged and stern woman she is today. The facts known by the night watch are a marked decrease in drug trafficking and battered women appearing on the streets. The fact known by Jayel is that she killed a man with her bare hands, and has never looked back.