From a personal standpoint, I wouldn't hesitate to remove them. Its just the right thing to do. How would you feel about a photographer than took a photo of you that you hated, and posted them on the internet and refused to take them down at your request?
From a legal standpoint, you are in a gray area. If you are ready to pay the legal costs of defending your right to display the images, and could case less about doing the right thing, then keep on trucking. You could probably win in a legal tussle, but it would be a hollow victory after you look at what it cost you to defend yourself.
I see a couple options;
Ignore her and hope she doesn't take legal action. You would probably win, but there is still a good chance you could loose. Throw the dice! Either way this could be an expensive option.
Offer to pay her so that you can display the images. She has a price, and its somewhere between .01 cent and 53 million dollars. Finding the price you can both live with is the key.
Take down those images, hire another similar model and re-shoot the same images. Changes are you will improve on the results, and like the images much better anyway. That would be my choice.
You could ask her what she doesn't like about them. You might be able to resolve it with some photoshop work.
You could reason with her in that if you can't use them for your portfolio, then you could be compensated for your time. Ie, if you asked her not to show any of the images because you didn't like them, where does that leave her? As a TFP scenario, both of you should be able to use the images in order for it to be fair to both members.
Lastly, you could slip her some memory altering drugs such that she will no longer remember who she is, or be mentally competent to identify herself. In that case you are free to use them at will. (disclaimer: this is humor, don't try this at home, at work, or anywhere
)