the end questions (spoiler)

The film I saw was dubbed so badly I couldn't understand a word of what Rospini said.







Spoiler questions:

1. who is the old lady and why did Ducci's ex-girlfriend write a letter to her explaining the entire crime. did she know she may be double crossed by Ducci?

2. why did Ducci kill her and not retrieve the incriminating letter?

3. why did the old woman wait all these years to then blackmail them?