What if Cersei changed her mind on Tyrion?

Let’s say Jaime rolls a Nat 20 on a Persuasion check when trying to convince Cersei to recant her accusations against Tyrion after she’s already ordered the Kingsguard to cease him for the murder of Joffrey. Would they be able to stop his sentencing considering that Tywin wants it to happen at that point? Or would it already be too far in the making?