The problem with rape as a crime is that it ultimately hinges on consent and an activity that may not leave a clear trace. Either party can lie about what happened and whether or not consent has been given, with the rapist claiming that nothing happened or consent was given when it wasn't or a person claiming they were raped claiming that something happened that didn't or that no consent was given when it really was. Often, there are no other witnesses or recordings of what happened, so it's a "he said/she said" situation.
In a society that assumes innocense until guilt is proven beyond a reasonable doubt, any woman making a rape allegation is required to prove something for which the evidence may be unclear and the most important evidence is her word. Don't be surprised if the guys get off here, even if they are guilty, because she not only has to prove sexual activity but non-consensual sexual activity. And despite what the judge might tell the jury, the fact that she came there to take her clothes off is going to create reasonable doubt over whether she'd consent to have group sex with a bunch of guys.
Consent isn't the issue for now- the players claim they did have sex with her period. If any of their semen is found to be inside the woman, their creditability is shot completely. If the semen doesn't match, it will be very difficult to make a case for rape, and depending on the what the photos actually show, difficult to make a case for assault and larceny as well.