In Gone Girl, Amy's neighbor Noelle Hawthorne comes to detective Boney and tells her that she was a friend of Amy. Next we see that while her investigation is going on, Noelle comes to Amy & Nick's house, but when the detective sees her at the door, she asks policemen to escort her out.
It was a complex case and detective was desperately looking for some solid information. Why didn't she question Amy's neighbor and friend? It is pretty evident that the neighbor hadn't told everything to the detective, because she shows up at the gathering and publicly discloses that Amy was pregnant. At this the detective seems shocked, but earlier when that lady was coming to her, she avoided her.
Why didn't the detective question her in detail, the first time?