Don't worry guys, she didn't get nerfed, she got better!
standard old build
Mercury tread, Hextech GB, Lich Bane, Rylias CS, Rabadons DC, Guardian Angel
boots->Hextech GB->sheen->BF sword/pickaxe->Iceborn Gauntlet->Mercurial Scimitar/Maw of Malmortus->Rabadons DC/Rylias CS->Bloodthirster Mercury treads whenever you want
This build is much more hybrid than the old build, but she will dish out even more damage and have more than twice the spell vamp and lifesteal. She will also be more defensive except for health if you pick Rabs (in which case you should get heath runes and masteries).
I believe that you should always get Rabs over Rylias because it gives you much more damage and you already have a slow from the Iceborn Gauntlet. Maw of Malmortus is a lot cheaper and gives practically the same AD but a little less MR, but with Merc Treads it should still be enough. The only thing is, I haven't tested the Mercurial Scimitar enough to see if the Active is worth it. If you get Scimitar get BF sword first and pickaxe for Maw.
Summary, A lot more damage, and can damage a lot for auto attacks. A lot more lifesteal. More Defense, but no revive, and less health.
I believe this is definately the best build, I have done all the math and it comes out ahead of the old one and any other new builds, especially since many of the old items got nerfed.