In the Harry Potter series, wouldn't the Elder Wand belong to Neville, not Harry? Since it belonged to Dumbledore, then Snape killed him, then Nagini killed Snape, then Neville killed Nagini, wouldn't it belong to him instead?
The Elder Wand never belonged to Snape.
"Severus Snape was never the true master of the Elder Wand. He never defeated Dumbledore. [...] the Elder Wand recognised a new master before Dumbledore died, someone who never even laid a hand on it. The new master removed the wand from Dumbledore against his will, never realising exactly what he had done, or that the most powerful wand in history had given him its allegiance ... The true master of the Elder Wand was Draco Malfoy."
-- Harry Potter, HP and the Deathly Hallows, Chapter 36: The Flaw in the Plan
The chain of Elder Wand masters went Dumbledore -> Malfoy -> Harry, not Dumbledore -> Snape -> Nagini -> Neville.
But if your question was more hypothetical (assuming that Snape had been the master of the Elder Wand, would Neville have become the master by killing Nagini?), the answer would still be no. Nagini was an animal and not a magic user, and could never have become the master of the Elder Wand. Her killing of Snape was on Voldemort's orders; Voldemort was the true killer. If Snape had become the master of the Elder Wand by killing Dumbledore, its mastery would then have passed to Voldemort, not Nagini, upon his death. This point is already covered in this question and this one.