If Selphie had been in her right mind, the chances are she would have attacked the imps anyway. They were horrible creatures, and probably up to no good. But she might have held off from killing them, at least immediately. Now, though, her only intent is death, and she sends a thundara spell to deal with both of the imps at once. But she was gaining pace on them, and would use her nunchaku if necessary to finish them off.