In keeping with her genealogy, leah being the spawn of diablo, and diablo being stronger than azmodan and belial (hence diablo being a prime), it makes sense that leah would morph into diablo, certainly influenced by his new power of absorbing belial and azmodan.
Edit = This is assuming that diablo is in the stone as well, i think op cut adria out all together so that sequence with kulle never took place.
Edited by Pyobe#1328 on 7/18/2012 3:43 PM PDT
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