Can you fix things your ex says are 'unfixable'?

My ex and I broke up because we didn't see eye to eye on something vital to our relationship.
In the breakup I said some really targeted things because she was saying hurtful things.
We are on talking terms, and although feelings are still there, she said she can't forgive what I said. I tried to explain why I said it. That she also said hurtful things too.

At this point we haven't talked for a month but she's still on my social media and is constantly one of the first to watch.

How can I fix things?
Can you fix things your ex says are 'unfixable'?
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