It sounds like what you want is to have the magical mechanism suspend the laws of physics. Don't know what you were thinking of in terms of how the character used the device, but I'm picturing something like a remote control with a stop, pause, play, rewind, and fast forward option. On stop, everything stops; the magical mechanism then creates an exception bubble for her, so those laws continue to apply. She can then point her magical remote at any random item, and turn on physics for that item/person alone.

If wanting to do this on a macro-scale, have her point the device at a miniature of the universe or planet or kingdom...etc.

As a slight variation, you could always have her using a 'beginners' version of the magical mechanism, which doesn't include a 'stop' button because 'stopping' the laws of physics will have interesting and long reaching consequences which pausing does not. A remote with a 'stop' button, therefore, is for those with advanced skill/training/experience/common sense/wisdom, etc.

It sounds like what you want is to have the magical mechanism suspend the laws of physics. Don't know what you were thinking of in terms of how the character used the device, but I'm picturing something like a remote control with a stop, pause, play, rewind, and fast forward option. On stop, everything stops; the magical mechanism then creates an exception bubble for her, so those laws continue to apply to your character. She can then point her magical mechanism at any random item, and turn on physics for that item/person.

If wanting to do this on a macro-scale, have her point the device at a miniature of the universe or planet or kingdom...etc. She could pause an invading army from the north, then spend two weeks leisurely sunbathing on a lush tropical island, before recruiting a bunch of her friends to remove all weapons from the invading army and replace them with salmon. The restart time, and watch the hilarity ensue.

Obviously, something this powerful should have limits incorporated into it. Limits of power or range or influence will give you opportunities to create interesting obstacles for your character to overcome.

As a slight variation, you could always have her use a 'beginners' version of the magical mechanism, which doesn't include a 'stop' button because 'stopping' the laws of physics will have interesting and long reaching consequences which pausing does not. A mechanism with a 'stop' button, therefore, is for those with advanced skill/training/experience/common sense/wisdom, etc.