Had Julie lied I'm quite sure it would have been revealed during cross examination at the trial. Any chink in her armour would have been exposed and the case would have fallen apart. It didn't happen that way though, Julie was a most credible witness, the defence failed to find any weakness or inconsistency in her story.
It's unfortunate that we don't have access to JM's trial testimony to see for ourselves exactly what was said.
How do we know whether jurors found her credible or not? The fact JB was found guilty by a majority 10 - 2 doesn't tell us anything about the individual aspects of the case and on what basis individual jurors arrived at their verdicts.
Also we have no idea how good, bad or indifferent Geoffrey Rivlin was at cross-examining and whether for whatever reason(s) he might have been awkward around opposite members of the sex whether in the witness box or not. We do know Geoffrey Rivlin quit advocacy a year of so after the WHF case to take on the role of full-time judge.