I heard an interview in which she said her cheating was Clapton’s fault for “enticing” her
All woman.
She may have made a mistake here.
I think the general rule is that while the recipient owns the actual letter, the sender still retains copyright in what he wrote. Depending on how much she intended to publish, she would have had to ask Clapton’s permission.
But ‘All Woman’ would have been to publish a book, but keep the physical letters to make another killing later :-)