Electra Ovilo is a veteran of the Titan War. Her love for Vincent caused them to have a short-term relationship, during which Vincent transferred the vaccine to Electra. She is unaware of this until Vincent sets free the Nanomachines on the Monorail and she survives. She meets Spike by chance when he infiltrates a bio weapon lab fronting as a pharmaceutical company where she works. After a few more chance meetings, and witnessing his being shot and thrown from a monorail by Vincent, she teams up with the crew of the Bebop to put an end to Vincent's intent to destroy the population of Mars.

The samples of her blood are used to make the vaccine that is spread over Alba city. In the end, it is she who shoots Vincent and kills him. She cries for him when he admits he remembers her and their love for one another as he is dying.
(Source: Wikipedia)