Guess I'm confused, as I didn't read about any attempt to remedy via a phonecall, that would have been my early attempt as I can understand not wanting to provide the info via email. Silly me, one time I got the number, code, etc, but forgot to get the zip code, had to call back. The only way I know to process without the code is if you have like a PayPal account and send an invoice for them to pay. If the renter is nonresponsive are you canceling the "contract"? Likely, there really is no contract as without charging the card, there is no consideration.
You cannot charge the card without the security code. The easiest way to avoid forgetting in the future is to charge the card immediately after you receive the information then tuck it away in the file folder for paid or deposit.
Now, if she did not stay, you simply cancle the reservation and don't worry about it.
If she did stay, there is a possibility for recourse.
But until we know...
Even at this late date you can charge a card if services or product was provided. Many card processing companies do not require a security code.
Since renter asked for her security deposit back, I assume, she stayed at your home. If you have proof of that stay, you can charge away even a couple of months later. Here's hoping her card is still active or good.