The number of spells is actually not a real problem, so she theoretically could have all of them. In terms of nerfing/limiting powers, the rule of thumb is that if there is some kind of game breaking ability (create gateways out of the world) or something that could be considered a "One hit KO" or destroy a city, then those are either nerfed or removed entirely.

So for example, for those who could ICly create some kind of portal to other worlds or realms, if kept the ability would be powered down to where they could only create portals to other locations of the city instead. Super powerful and destructive spells could still be strong, but rather than taking out a building in one shot it would just leave a lot of damage, possibly blowing a small chunk out of the wall.

Anything else could actually be left alone, but if you're still worried, another way to nerf some of the more high level spells is keep them intact BUT limit the number of use somehow. Perhaps it would be more draining on them, or there is an actual number cap.

Hope that helps! If anything, we'll let you know if we need a certain ability tweaked.