Eh it's hearsay but there is a way around it, the testimony wouldn't be about what happened but what she heard someone saying happened. Which yes is obviously is hearsay about what happened but witnessing people's reaction to an event is still a legitimate thing, nowhere near as strong as actually witnessing it. What you're also clearly missing is that obviously this is basically worthless on it's own you'd need other evidence for it to be effective, like I don't know his fingerprints on the wheel, not an actual thing, just any kind of bits of evidence that also support it strengthen it and work together.
Obviously all we really have is a hearsay story that's it could be true could not be she testified under oath that she heard it. The secret service who would have actually witnessed it refute the story, and that would strong evidence against it, if they actually testified under oath. Their refusal to do that while she did really makes this a wash to me.
So am I still eating pancakes or not?