It’s the other way around, actually.

In The Amazing Spider-Man #125 (Oct. 1973), Marvel Comics editor Roy Thomas wrote in the letters column that “it saddens us to have to say that the whiplash effect she underwent when Spidey’s webbing stopped her so suddenly was, in fact, what killed her. In short, it was impossible for Peter to save her. He couldn’t have swung down in time; the action he did take resulted in her death; if he had done nothing, she still would certainly have perished. There was no way out.” Source

The comic (#121) is ambiguous though. There is really no way for the reader to know whether she was dead before her neck was snapped, Green Goblin certainly seems to think so (but he is hardly a reliable source). But snapping her neck certainly would have killed her anyway.