But I get frustrated with her from here onwards, as this is just the first of the chances she will pass up to be rid of the visions, even as it becomes increasingly clear that, as Groo pointed out, a human literally cannot bear them. Her attachment to the visions becomes downright unhealthy. I share Angel’s anger over her concealment of her medication-dependency and brain scans ("Birthday"). She knew she was dying because of the visions, and she didn’t think that she ought to inform her friends...? Maybe she thought that they’d suggest trying to find a way to remove the visions, which would be, oh, the sensible thing to do! What was Cordy hoping to achieve by martyring herself for the visions? Forget the hypothetical “needy”, what about her family, or at least her friends, who loved and needed her? Her behaviour was pigheaded, and frankly selfish.
Somebody with average abilities, but a commitment to doing good till the end, like Xander, or Anne, is worth more to the forces of good than somebody who is highly useful for a couple of years, but then burns out, becomes comatose and dies as a result. Groo could have borne the visions until old age (not sure about half-demon lifespans....), which is another reason why Cordy would have been better off entrusting the visions to him. Skip cleverly plays on her ego by showing her Angel voicing her own deepest fears: “Cordelia is not a champion. She is a rich girl from Sunnydale who likes to play superhero. She doesn't have what it takes to do this!” Thus – her pride wounded – she is determined to prove herself strong enough to bear the visions – becoming a demon in order to do so, in spite of Skip’s clear warning: “And even after the pain subsides the effects of the transition will be numerous and unpredictable. You may never be able to lead a human life again." I would never say that she deserved what happened to her - no-one would ever deserve that - but I will say that her ego and martyr complex played a part in her fate.
In a way, Jasmine, with her overwhelming desire to “help” people – albeit regardless of their wishes – and her faith in Angel as her Champion, is an exaggerated version of Cordelia herself. Cordelia’s possession by the PTB is just the final step in their use of her as a vessel - a process she complied with every step of the way. Jasmine is not entirely untruthful when she tells Connor that she is realising the world Cordelia dreamed of, although of course the real Cordelia would never have hand-waved the eating of people, nor the removal of free will. But Jasmine does use Cordelia’s body to help more people than the mere mortal Cordelia could ever have done – just at a price. Be careful what you wish for....?