For me, "Ela disse que tinha esquecido" sounds better
Duoligo should allow 'that' without taking my heart!
Beta version has many mistakes. Just report them :)
If isn't there a person how I can recognize that she said about itself or about me? (Eu tinha/ ela tinha) Should "I had forgotten" be accepted?
That's the point: when you do not use different pronouns to tell them apart, it means they are the same.