Translation:Ela disse que viria hoje.
Alternative answer given is 'ela disse que ela viria hoje'.
I thought you would never use pronoun twice in one sentence?
It's optional. It's better to save subject pronouns in the formal writing. But generally we don't omit the pronoun of third person in the spoken language.
When the referred person is a third it's better to explain that they are the same, because it could be another third person... "ela disse que o carteiro viria"
In a context, it can be unnecessary