My cat keeps pouncing at my rabbit but it just started?

we got a rabbit from a shelter a few months ago and we have two cats the oldest one flo started jumping at the cage yesterday even tho before she never bothered him now shes started jumping at the cage idk y we have had problems with her killing pets she has killed one bird then her and our other cat killed the second bird we figured she would realize she cant kill the rabbit cuz hes too big but now idk whats going on and our other cat optimise prime keeps wanting to climb up on the cage and lay down on it hes not trying to be agressive or hunt i think hes just curious anyway what do we do to get flo to leave him alone and optimise to stay off the cage thanks for the help and no rude or nasty comments