I don't think it's Alice's responsibility to demonstrate her worth to her co-workers. If the company really thinks Alice is that much more valuable, they should easily be able to demonstrate that to Bob, Fob, and Gob. E.g. Alice should have more responsibility. If the company can't explain to Bob, Fob, and Gob why Alice is better, I think that's the company's problem and Bob, Fob, and Gob are right to be upset.