I think it's reasonable to question whether she should be allowed to compete. But this post is wrong. She's not 'a man.' She doesn't have a penis or '3x the testosterone of a woman.' Or if she does, it doesn't have the same effect it would in a normal man's body. Pretty sure she has androgen insensitivy syndrome, meaning that she has XY chromosones, but the body is insensitive to testosterone's effect. In Atlanta Olympics, it was found that there were seven genetically male athletes with AIS. They were allowed to compete. So, this is issue is not unique to Caster.
They don't just let them because they 'feel like women' either. The evaluation includes analysis by an endocrinologist and gynecologist. Fair question though to ask whether such people should be able to compete as women. No one really knows what the physiological advantages are and to what extent they exist.