Here, Gwen willingly has sex with someone who everyone in the world knew was bat-shit insane.
Not exactly. Only Peter knew at the time.
And I'm not officially clear on Goblin history, but Ben Urich wrote the "expose" book on him after Norman's initial "death", which Norman debunked when he returned. He was only officially exposed worldwide as the Goblin after the events of The Pulse.
So there's nothing to indicate that Gwen knew that Norman was "bat-shit insane" at the time of their sexual encounter.