One solution: what happens while world is frozen is not real (yet). It's illusion or simulation or dream of some kind. But any actions taken during that time will happen when time returns to normal. Set ball rolling, and it will start rolling for real. Open a door and it will begin opening for real. It could be some kind of a phantom force, which mimics what was done in the frozen time.
Of course simulation/dream would not be perfect, and the longer the frozen time, less accurate the phantom force would be, as real time diverges from it. So undressing someone might be impossible (it might happen in frozen time, but in reality it might end up resembling pulling victims clothes in wrong directions), but pulling their shoelaces open quickly would work. Opening a door or simple latch would work, but using a key to open a lock would most likely have the key missing the keyhole and dropping to floor (the lock might or might not still open, most likelydepending on the phantom force acting without the real key). Etc.
So how would the frozen time work then, is your actual question. I'd go with, what ever seems "logical" to protagonists brain. So things will be as she believes they would be if it was real time. It's up to you if things actually reflect reality, so she could open a sealed letter and read it, or if she would just see nonsense if he doesn't know what is written. And things would probably be frozen unless she actually touches them an wills them to not be frozen. This would give a lot of freedom to have things appear pseudo-logical in the frozen time, without stretching suspension of belief, when things would then happen realistically (apart from the existence of the supernatural phantom force) in the real time.