I find it more strange that Melody Stanton heard a scream rather than that the Ramsey's didn't hear anything. They were three floors higher, almost 7000 square feet, carpeting, doors shut, etc. Although I don't believe IDI, I can definitely see how JBR could be killed in the basement and no one heard a thing. Also, I know the houses on their street are close together but I always found it weird how Melody Stanton actually heard JBR scream. The houses on my street are pretty close too and I NEVER have heard things going on INSIDE my neighbor's houses. And didn't Melody Stanton dismiss it as, "Oh JBR's just having a nightmare"? Doesn't that sound like maybe that wasn't the first time they heard screams from the R's house? And how did they know it was JBR? Was she the only little girl on the block?
I also think that the reason she changed her story was either because of the R's "people" or the media getting to her; most likely, both.