This is what we know from reports:
1) The victim called 911 and said she was being assaulted.
2)the victim recanted and said she lied on the first call.
For anyone to claim they know anything more, means they know which of the two times the reporter lied. (Its possible to speculate, but only two people have first hand knowledge of which was a lie).
As far as prosecuting Miller, if the woman who called 911 is willing to testify that she lied on that call, and told the truth the second time, this creates a problem for the prosecution. One choice they have is to not proceed. The other choice is to proceed and attack her on the stand. The conundrum for the prosecutor, is that they believe she is already a victim, attacking her on the stand makes her a different kind of victim. They may not be willing to do this. If they go forward with the prosecution, and they attack her on the stand, and they lose the case, its an unmitigated disaster on multiple levels.