"this was the issue in which Spidey broke his girlfriend's neck, right? "Wrong. I'm not sure where you got that idea from. In the previous issue the Green Goblin killed Gwen Stacy. In this issue Spidey gets revenge and the Green Goblin dies, though not at Spideys hands.
Gwen's death DID happen in the previous issue [#121] but she died after the Goblin knocked her off of the George Washington Bridge; and after Spidey caught her with his web-line only to have the whiplash snap her neck as a result of the impact from the fall.