Just because you are unable to see it doesn't mean it's not there. She is wearing the necklace.
So you have seen the original video from the DVR - as both the def and pros has and do not refute - not the screenshot from a video broadcast over the internet displaying a video shot from a camera and displayed on a screen which is at an angle to the camera.
There are at least six opportunities for distortion of the image:
1) the original capture was compressed to save space on the DVR's hard disk in a format such as MPEG-2, MPEG-4, H.264, or WMV
2) the video was transcoded to MPEG-2 to play on a DVD player.
3) the video was played back by a computer on to a projection screen
4) the video was captured by a digital camera positioned at an angle to the projection screen in MPEG-2 or MPEG-4 and stored on the media pool's HDD.
5) the video was transcoded to an internet-friendly format such as MPEG-4 or FLV
6) Otto took a screen shot and saved it to JPG format - a lossy image format.
All of the above compression formats are lossy formats. That means that with each transcoding operation information is lost and noise and other artifacts are possibly introduced and enhanced.
There is NO WAY to conclusively determine from that screen shot that there is a necklace on her.
You are seeing the digital equivalent of Jesus' face in a potato chip.