I don't think she's lying. I think she is just confused about what really happened. She could have been raped more than once and can't get the stories straight.
Rape is a really tough thing to prosses and some times the victums can't handle it and some others can. Every person and victum is different.
You don't have to listen to what she has to say or believe her but be supportive cause if she is telling the truth, she's had a hard life.