It means she's proven her usefulness to the Commonwealth in a way we wouldn't have thought possible months ago.

It was the Wampyr's last chance to prove their usefulness.

I shall prove my usefulness, even if the Earthmen do not think of me as a warrior.

Yet he proved his usefulness to the last.

And the boy had proved his usefulness by scouting out places no slave could hope to penetrate.

The phone had proven its usefulness in the real world.

This code has proved its usefulness but is deficient in two important areas.

These two agreements have proven their usefulness in the past.

To begin with the first question, the funding facility for balance of payments problems has proved its usefulness in the past.

Even if a candidate moves with relative ease through the process of proving its usefulness, no new drug can be expected soon.