In the U.S., one can waive the right to an attorney; in Italy one cannot.
So it becomes clear that, from your point of view, expecting the police NOT to entrap a suspect is a "fantasy idea of how the law works."
Let's talk some more about whether or not they would be likely to plant or fabricate evidence.
I don't think you quite understand how the "right to an Attorney" works.
Just because in Italy, one is legally required to be provided an Attorney does not mean one cannot open mouth, insert foot at his, or her, insistence with or without an Attorney present.
Somewhat like Ron White's bit:
"I had the right to remain silent...but I didn't have the ability"
Amanda had the right to remain silent and the right to consult with an Attorney (an Attorney was even legally required to be appointed to her) - but she made the choice to do neither. That is why her statement was considered admissible - because her rights were not violated.
Amanda clearly, and insistently, demanded that she be heard - without regard to her right to have counsel present. Regardless of what country you're in, that's a foolish thing to do - but it was not in poor style for Mignini to take her statement.
I dare say, she's had better luck with her Italian rights than those that would have been afforded her here in the U.S. See, here in the U.S., you have rights - but you can waive those rights at the drop of a hat. In other words, when the Officer places you under arrest and reads you your Miranda Rights, anything you have said previously and anything you say in the future can be used against you in the courtroom. That is simply not the case in Italy - and for that, Amanda should be quite grateful.