Two separate questions. The jury is charged with evaluating the credibility of witnesses. That is their job. They will assign credibility to Rachael's testimony as they see fit. I suspect the figure she is not trustworthy under the circumstances.
But nobody came right out and said she is a liar. It was pointed out that she shaded her testimony when in the presence of Sybrina, that Sybrina was present for the Crump interview and the state's deposition. It is said that she is Martin's friend, which gives her a motive to lie to cover for him, etc. People lie on the witness stand all the time with no penalty beyond the jury thinks they are lying.
If Crump is guilty of manufacturing evidence, somebody has to produce direct evidence of that. If Rachael admitted that in this trial, it would produce cause to charge Crump, or de la Rionda, or whoever helped manufacture the false evidence. Rachael would get swept up in that too. But, prosecution would be under a different trial (not that the state would press charges against itself).
Again, your explanation makes a lot of sense, and I do appreciate your taking the time to explain this to me, because it was something that I did not understand.
The fact that she couldn’t read a letter she was supposed to write indicates that someone was manufacturing evidence.