Remember you are the victim. You have nothing to feel guilty or ashamed about. After a rape, survivors may be openly upset, even hysterical, or they may be numb and seemingly calm. She may particularly need medical attention in the first three days. She should obtain SDT testing, a pregnancy test, counseling and treatment for injuries.
Rape is a traumatic violation of a person.
Stay with her and find supportive people for her to turn to. With date rape especially, victims need to be believed that what occurred was, in fact, a rape. This is a very important fact in recovery. Don't blame her or agree if she blames herself. Even if she made some bad decisions, no one asks to be raped.