Since her introduction as Gwen Stacy, first love of Andrew Garfield's Peter Parker, fans fell in love with the quick-witted sassy blonde. She made us laugh talking back to Spidey, and broke our hearts when she asked Peter why he was at her dad's funeral. She is who everyone wanted Kirsten Dunst's Mary Jan Watson to be in the Sam Raimi Spider-Man trilogy. She's not helpless, but still needs our hero to save her. She is the one person throughout the movie that everyone is always rooting for. Losing her would break the heart of the entire audience, which is exactly why she has to die.
Peter Parker changes when Gwen Stacy dies. As much as he grows to love Mary Jane, it always was and always will be Gwen Stacy who stole the web-slinger's heart.
Every forum having anything to do with The Amazing Spider-Man 2 has comments on comments on comments about how no one wants Gwen Stacy to die. Personally, I like the way Star Trek changed the who lineage of what happened and what to expect within the first 10 minutes of the new movies, I don't need everything to be canon with the comics or the original. That's not why Gwen Stacy has to die, although it will please the die-hards, she has to die so Peter can finally grow up. He's able to be happy with Gwen, to joke with her, to laugh with her, to be a kid with her. When they're together he's not a super hero, he's just the happiest kid in the candy store. They have the kind of first love we can only dream of, which is why we so desperately want to see it work. Gwen's death will mark the death of whom Peter Parker is up unto that point in his life. And will mark the birth of someone brand new, a mature, hardened Spider-Man.
Emma Stone, you have been amazing, and I hope there are new flashbacks with you in it for many movies to come. You made me hate Peter when he hurt you, and made me fall in love with you on my own. You are Gwen Stacy, the best Gwen Stacy we've ever seen, and the first Gwen Stacy that will pop into our minds. You are going to make this the best Spider-Man series of all when your neck snaps at the end of the web. RIP Gwen Stacy, we owe you one.