it looks like a spider walking on its web, but just too close to the screen to be visable which makes it blurry.
i think unless something abnormal happens to me, i might think otherwise...but im a little bit skeptical.
If you run across a video camera or camera it leaves trails sometimes which some may mistake for a spirit, there could be too much light somewhere in the distance and makes an "orb" which some also think is a spirit.
The OP story seems a little ... odd.
It sounds exactally like the movie Shudder.
A woman and her husband driving down streets of Japan [i think]
Woman sees a girl -in white
Woman tries to stop so she does not hit her, they swerve, hit the girl, when they go to look back, no girl.
Maybe your friend has watched too many horror movies that have a fimiliar scene like this...