I think it's preposterous to test her only after she won the race. The doubters should have had to question it before the race.
But, any time there's a "gender confusion" involved in these sporting events, reasonable analysis always suggests the single best course of action: Make women and men compete together.
Most people think we should be able to get a nurse to look at someone naked and say M or F, but the gender test involves several different evaluations: genetic, anatomic, even the say-so of a psychiatrist! It is entirely a subjective judgment by a group of "experts". The reason of course is that sex or gender are both themselves subjective terms. Is it the body parts you have or the genetic make-up that make you one or the other? Usually they go hand in hand and there is universal agreement. BUT not all the time, especially when it comes to women of extraordinary physical attributes...predictably.
For example, there are people with XY chromosomes who appear female, and all sorts of anomalies. Solution: make all the freaks...excuse me ATHLETES...compete with each other.