Of course the big question is "Just exactly what is Pluto trying to 
accomplish here?"  She's either incompetent, or she's fiddling to avert 
something.  

The thought occurs to me that her goal may be to prevent Misako from 
becoming the next Nephrenia.  She was well on the way to becoming a 
deadly enemy of Usagi, when Usagi finally takes the throne.  Does that 
mean that there's a villainous Misako in the future, who is in the 
process of being erased?  

On the other hand, maybe Pluto's just a screw-up.