Keep in mind that we know her power acts to protect her well before a threat pops up. It's entirely possible (and in character) that if let go, Coil would run like hell, set up somewhere else and then a while down the line start wondering 'oh hey, maybe if I'm way far away and maneuver people to hit Butterfly rather than doing it myself, I'd be safe?' This may well be her power preemptively going 'nope'.
Also, consider what this means for Coil's activities. He keeps his lairs, he keeps his resources and he keeps his connections. After all, he'd need all the resources he can get in order to improve Taylor's life. In fact, there's very little that her power changed for him beyond 'don't go after Taylor'. Hell, he can even take over the city if he wanted to, provided doing so doesn't harm Ms. Hebert or her father. Her power might even help him out if he does so in a manner that improves the Hebert's lives in some manner.
Keeping him in the Bay keeps this demonstration in mind. Keeping him active keeps him focused on not trying to screw Taylor over if he gets tricky. Because god knows memetic Coil would do something stupid after he had a while to get over his trauma. At this point, it's all trauma all the time.
Basically, it all comes down to whether or not you believe that her power (or Ziz) is acting to protect Taylor, or to improve her livelyhood. Considering that we've seen things happen to prevent minor acts of bullying, but nothing has happened to measurably improve their lives (no, preventing harm != improvement) until Coil, I would assume that it's actions fall under protection.
