Mmmm, I have to go along mike781 here- I think it's pretty clear from the dialogue and her personality that she'll want to show off a little and use the most impressive stats on hand- 3 awards in 20 years sounds probably more impressive than "just" 3 in 50. Plus, no one really includes time before their birth, unless they add something to the extent of "no one, apart from me recently managed to..." Whilst the dialogue implies that she personally participated in 50 contests (or more/less, depending how often they take place) throughout all these years. And it has been hinted before in TRPG2 that Shadowlings live for much longer than humans, so 50 years might seem like a little time to them.
The way Shadowboxer and Darkling refer to Nelis, and the implication that she lived for thousands of years is indicative of Shadowling lifespan being much shorter, say in the lower hundreds (they mention rumours, almost myths, that she created a Shadowling race, and look at how much Nelis is different physiologically, at least outwardly, from the other Shadowlings- surely both these things take a lot of time and a lot of generation changes of species to take place?).