Isn't autobiography a written account of autobiographical memory?

No: one could easily imagine a world where you remember all of the bad stuff, but are still incentivized to not write it down; an autobiography is an edited work of text, while autobiographical memory is a capability of a human.

Yet autobiography is written by the person telling her own story.

You could remember bad stuff but you are not incentized to write it down.

Then how are they both different?

Dude, it's saying the things you remember about your history are biased positive. There is no writing down, there is no telling, there is no other person involved here. You are remembering your own past. In this past story, you bias positive in the things you remember.

And when you remember it positively, would it not translate to written autobiographical accounts to be biased?

Won't there be a correlation?

Or am I missing something?

Your memories are a function of what actually happened. What you write is a function of what you remember. Two separate processes.

Bias on how you retell your own story is, as you say, a fairly obvious concern, so (for the purposes of this discussion) written autobiographies being biased is completely uninteresting.

Rather, it's the fact that your recollection of events biases towards the positive that's the novel, interesting information.

So you agree there is a correlation and yet you somehow disagree with me. Let's agree to disagree

Yes, there can be but here try to remove the context of writing it altogether. You tend to remember positive memories more than negative memories. That's how our memory works. Period.

Autobiographic memory and an autobiography are two different things