There are two issues with assuming that Harvey is talking about Shakespeare when he refers to an 'excellent gentlewoman'.
Firstly, at the beginning of his career, Shakespeare was largely unrecognised. In 1593, he was likely still living in London and would not yet have the profile to draw the attention of the country's most prolific literary critics.
Secondly, by 1593, Shakespeare had written more than three sonnets and a comedy. He had written five plays himself, co-authored a further three and written two long poems.
Therefore, we can assume that Harvey is not talking about Shakespeare when he refers to an 'excellent gentlewoman'.