If she'd known, she'd know why Peter wasn't at his place and instead of waiting around for him to come back just go home and see if Spidey was okay on TV. Thus, she wouldn't have been there when the Goblin came to Peter's place looking for HIM.
Absurd. Gwen died because of the point you want to miss: anyone--hero or villain--poses a risk to civilians by knowing they are a part of the hero's private life, while civilians in on the secret are placed in greater danger, like Gwen or Iris West Allen. Osborn--Hell bent on revenge-- would continue to canvas the city if no one was at the apartment, and knowing all about Parker's civilian life, he would target someone else to use in the manner seen with Gwen. The civilian knowing Parker's ID would not protect them from a superpowered madman's hunt/attack.
Further, its cartoonish to think his civilian family/friends are going to live a life where they are constantly disrupting their regular lives to be on high alert whenever yet another villain in on the secret is on the rampage, escaped prison, etc.
Illogical and as always, creatively bankrupt.