Well for one, it looks like Maul is in the middle of jumping at her and perhaps her control over lightning isn't strong enough to stop him in mid-air and throw him back.
In that particular instance, we can't use Dooku flinging Anakin across the room as the norm because Sidious was blasting the shit out of Luke and all did was fall, as opposed to flying back. Mace was being cooked for a good 20-30 seconds before being flung out the window. This leads me to believe that the motion of victims being thrown is more of a TK feat rather than an effect of lightning itself.
So really, there's nothing to suggest that Maul wouldn't continue his path of trajectory even after being struck with lightning. But perhaps he knew how to redirect some portion of lightning that he comes in contact with.
Either way, the Nightsister's power is likely far below that of Kun, and were he to hit Maul with lightning (or some variant) I doubt Maul would react the same way he did with the Nightsister.
But that would be hard pull off with Maul all up in your face trying to kill you.