Sandi Gibbons from the L.A. County D.A.'s office tells us, "We deal with her attorney who says she is a cooperating victim."
Even if Rihanna clams up, the D.A. is used to prosecuting these cases without a cooperative alleged victim. That's especially true in this case, where there are graphic photos (the worst of which have not been seen), along with Rihanna's statement to cops that Brown has beaten her before and the violence was escalating.