Progressives were probably almost all going to vote for her just because of Trump. The real gain a VP can get her is in the Independents, which is now huge. If she can do that, she doesn't need a single moderate Republican vote.
You forget, dear boy, that the among the "independents" are many moderate Republicans.
And if she had taken a more positive step in the direction of a progressive agenda she would have attracted a much more robust and growing base.