I think she could easily win the GOP nomination if she wants to. Yet, given the numbers, there is a chunk of the electorate who will not vote for her in the general election without a change in perception about her image and credibility as a presidential candidate.
I am not sure what it will take for her to improve her image with those people she needs to appeal to, but she needs to concentrate on doing that if she wants to win the general one day. I said a few days ago serving in the senate would be one way of doing it (worked for Hillary and Obama). However, it doesn't look like that's what she has in mind.
“I am not sure what it will take for her to improve her image with those people she needs to appeal to”
That’s the thing. I think she took care of that when she resigned. The only thing left is sheer force of personality.