CarolDanvers exactly the same here.
I feel sympathetic in terms of yes she probably didn't know initially, and her whole sense of self probably rests on what a superb athlete she is, certainly she has likely worked as hard as other athletes, trained to ridiculous levels etc and I suppose the question marks over her testosterone level probably feel like all of that hard work and dedication is entirely negated. No doubt it would be frustrating to feel like your athleticism is being pinned entirely to your T if you feel you've worked hard to achieve what you've achieved too. But ultimately, even if she didn't know, she wasn't competing fairly and as pp have said at the point you do know that, you should step down, soul destroying as it would likely be.
I'm concerned that the emphasis on testosterone risks the fact that male puberty confers advantages is lost. I can imagine a future where everyone concedes testosterone is important so trans athletes suppress their levels - but continue to do well due to the biological advantages of a testosterone fuelled puberty, at which point their success is used by activists to show "see, T doesn't mean anything". I need to read up more on the lifetime effects of T and how much these are diminished by suppressing it.