Greed is genuinely NOT GOOD no matter which way you swing it. Greed on a scale that deprives others is infallibly evil. Vivi is greedy.
But of the seven deadly sins Greed is invariably depicted as the most positive... Quibble aside, I already denied greed as a primary motivation.
Wrath is chaotic. There is no law in unbridled wrath. Vivi wants the party to suffer. Vivi is wrathful.
Which I agreed with.
Also, in retrospect, an interesting potential motivation for her wanting to summon Rael would be if he promised to recreate her sister somehow; that's probably not outside the realm of possibility for him.
In any case, I think it's far from clear-cut that she's outright evil.
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"As the size of an explosion increases, the number of social situations it is incapable of solving approaches zero." -Vaarsuvius, Order of the Stick