Don't refund the money she already paid you. You earned it. The question is whether to fight for the unpaid portion. That's something you just have to decide based on your own priorities. It sounds like the most important thing is putting an end to this relationship--some client/freelancer pairings just don't work out. That's okay.
If you want to fight for the money, submit the next milestone, since she's only paid you 50% and you've done 90%. If the next milestone if for the full remainder, you can change the amount requested to reflect what is actually done. Maybe 10% for the part undone and 10% for whatever revisions would have been needed for the home page, but you'll be better able to figure out what's appropriate.
If you just want to be done with it and don't care about the rest of the money, close the contract. She's likely to be unhappy and may leave you negative feedback, but if you close the contract yourself, there's a chance she won't bother to come back and leave you feedback. You'll keep the money she already paid and the rest that's in escrow will go back to her.
You're top rated, so if you haven't used the removal perk recently, you can always delete any negative feedback she might leave you.