I could not agree more with BeenBurned's post.My opinion is going against the majority here.
There's no doubt the shoes were used and no doubt that even though the pictures are blurry, at least one of the pictures showed damage on the side of the sole and another a damaged sole. And in the description, the seller implied the rough shape in her "Pictures and Price Reflected."
But what bothers me most is your first message to the seller that specifically mention the "many reasons" for negging her.
She immediately responded that you could return the shoes for a refund. (And in fact, that message TWICE mentions to return for refund.
And again, you respond that you'd rather neg than return and lose money on shipping fees. (She never mentioned that she wouldn't reimburse shipping, but it seems you were intent on negging from the beginning.)
In both her messages, she said to return. What more can she do? And you still want to neg her?!?
I'm sorry based on this case, I don't think any feedback is appropriate. But negative feedback (or even neutral here) are inappropriate because the seller has done (or attempted to do everything right) and you aren't willing to take her up on her offer.
Either the shoes are good enough to keep, in which case there shouldn't have been mention (twice) of negging or they're not good enough to keep and you take the seller up on her offer to accept a return (an offer made three times in two messages).
If indeed you were offering constructive criticism to the seller about disclosure, feedback should never have been mentioned. In fact, you might find yourself in hot water should she report feedback extortion.
I'm sorry but I do think you're wrong.
I can empathize with your frustration, but I'd say a neg is ultimately uncalled for- it's not like she listed the shoes as new or in perfect condition or is refusing to work with you. The listing photos clearly show the shoes are not in like-new condition and she's offered multiple times to take them back.
You won't return them and I'm really wondering what would constitute a happy resolution of this transaction for you? You made the choice to spend money having them cleaned before you let her know you weren't happy with their condition; I'd hate to see a seller who seems totally willing to try to work with you get a neg because you've already decided there's nothing she can do to make you happy.
Why contact her if it's just to rub the neg in her face and you don't actually want anything? I'd be enraged if a buyer sent me messages about everything they thought I'd done wrong, then refused to entertain options for a return/resolution. Sure, she's not being super friendly about it (not a classy move, in my opinion) but I might have trouble being polite in this scenario as well.
I also agree with BB that much of the content of your messages to the seller sound a lot like feedback extortion. Again, how could she resolve this situation to make you happy, since she obviously can't hop in a time machine and re-write her original listing? What are you asking her for if not a full return? If you're not giving her options for her to resolve this with you, I honestly don't get why you'd even bother contacting her at all. Also, OF COURSE she's trying to protect her feedback- if I were her, it would be the only reason I wouldn't just tell a buyer in this situation to eff off. She's not looking for some sort of 'teaching moment' with a disgruntled buyer, she's trying to actually resolve the problem and protect her status as a 100% FB seller. IMHO, she's doing her best to be civil and accommodating and you're not working with her.
I'm honestly sorry this transaction was not a happy one for you - I know ebay can be very maddening in this department. If I were in your shoes (heh), I'd return them and chalk this up as a lesson learned: ask LOTS of questions before buying pre-owned items that are clearly not in pristine condition. Maybe a neutral is called for here, but to me, even that's a stretch. Good luck working this out; I hope it goes smoothly for both parties from here on out.