She retracted the accusation that very day, then again the next day. It's not her fault that the police and Mignini refused to listen to her. Don't forget that Lumumba being the killer was the police's theory - they believed it before they made Amanda sign the accusatory statements, as was clearly stated by police chief De Felice. They had a witness (falsely) state Lumumba's bar was closed earlier in the evening. They (falsely) claimed Lumumba had switched phones after the murder and lied about it. They (falsely) claimed Lumumba couldn't give a good explanation for why his bar's first receipt was stamped ca 22:30 if there were customers there earlier. And when a Swiss professor came to Perugia to give Lumumba an alibi, they got a "tip" that (falsely) said the professor was a criminal. Nothing of this came from Amanda - it was all the police's doing, and it's documented. When the depth of their error was evident, Amanda became a convenient scape goat.
On the contrary, she repeated her accusation and it is precisely on this that the court will now rule on.