Yep, Faye is correct.

And it isn't that hard to get 100 Cursed Spikes.

Travel to Island closest to Hell, or is it Heaven??
Anyway, the one on the east side of the world.

There you'll face Tri-Face and Malboros, that can both give you C. Spikes.
Mug the Faces and don't mug the Malboros.


Someone once said that Siren need to be at lvl 100 to be able to refine, but that isn't necessary, atleast not on the PC-version.