It has not been established that she lied. Read the PH. Prosecution stipulated only that Feldman had affadavits from two witnesses to "impeach" Brenda, not that they were true and correct. AND the prosecution stipulated them only for the PH and specifically not for trial. Meaning, prosecution reserved the right to dispute them at trial and possibly "impeach the impeachers".
The stipulation was procedural to speed the PH, and indicates nothing about the truth of the matter.
The defense is going to have to show that the witnesses knew DW and Brenda well enough to identify them, don't have axes to grind, and are credible witnesses of the truth. That they arrived at the bar before DW left and after the dancing started. Brenda claims to have danced with an older gent whom she knew slightly, but couldn't remember his name (I couldn't quite understand if she meant at the time of the hearing, or at the time she danced with him, and it wasn't pursued). This leaves doubt about what the "witnesses" saw, or what they think they saw. What if they don't know DW, really, but claim to recognise him as the man she danced with from t.v. coverage, but it's really the other guy.?