Complex sentence: He convinces her that she does not need to forgive her parents for abandoning her in her childhood, but as an adult, to have the maturity to see her parents as two regular people who are driven to make mistakes, like everyone else.
Split into simpler sentences: He convinces her that she does not need to forgive her parents for abandoning her in her childhood. But as an adult, have the maturity to see her parents as two regular people who are capable of making mistakes, like everyone else.