I'd assumed from all the fuss it was a trans person but as far as I can gather it's just a mannish woman. I'm not sure why she was banned from competing before, supposedly not a testosterone issue but if it was explained why it was it would clear things up somewhat.
The backlash seems harsh on her to me, she can't help how she was born, but I don't know all the facts. I don't see it as being much different to the Williams sisters using their extra height and strength to bludgeon their way to victory repeatedly.