Edit: I think I know the significance of Britney walking the halls in a white shirt with glowing lights behind her right after she seemingly drowns in the bathtub. I think that the Britney in the white shirt represents that part of her that died when she had the abortion and now that part of her is restless like a ghost.
When this song and video were released, people were perplexed as to the symbolism, especially with respect to the baby at the end. Now that Britney’s memoir has been published, of course, we know now that Britney became pregnant during her relationship with JT and he basically pressured her to have an abortion (using the abortion pill, which is so dangerous to women I can’t believe it’s legal). This song came out right after that incident. It is clear now what this video is depicting. I pray for peace for Britney and the baby she was forced to abort.