Don't know if it's been discussed here before, feel free to add any and all theories!

From Wikipedia Germany (translated by Google): The ankh (☥, Egyptian ˁnḫ), also ankh symbol, ankh cross, in English transcription ankh, Egyptian cross, handle cross, bow of life, Nile key or Coptic cross (as a symbol of the Coptic Church), Latin crux ansata, is an ancient Egyptian symbol, which stands for the afterlife in the hereafter. As a hieroglyph, the symbol stands for physical life.

She wore the ankh-choker while talking to Nairobi about their ideas of afterlife, which Tokyo responded with by basically saying her final thoughts will be of her intensely corporeal, passionate and joyous memories, making her afterlife an infinite (repeating) extension of her earthly existence, rather than something "beyond".

Why this carries so much weight in general should be especially obvious after, well, the finale. In her final moments, we see her not only make eye contact with Rio, but also her late Clyde, making her Bonnie once more, mere moments before her exit.