Why did the girl and the guy who helped her lie?

When they went to court, they both claimed the witness said the guy moved strangely or suspiciously (translation problem?) and had not said it wasn't him. The witness did say it wasn't him and never said he moved strangely. So they both lied twice. When the witness was located, shouldn't that right away have discredited their testimony since it doesn't match what the witness claims or the girl's initial statement?

I don't get why they threw that in unless they wanted to make the girl look bad. There seems no reason for her to lie unless she didn't care if he was guilty or not and wanted him to go to prison regardless. One can assume that maybe the prosecutor told them to say that in case the witness was located. And if that's the case, that reflects even worse on them.