Even if she is offered money, should she decide NOT to have sex and it is forced upon her, it is still rape.
She can opt out should she wish according to the law, as she should be able to.
Looking at the facts here, and if they are as the victim stated, she was the victim of a gang rape. There are other charges too. The involvement of a gun makes it an assault with a deadly weapon. There could be false imprisonment and kidnap also.