Just ignore her harassing emails and block her emails or send them directly to your email trash folder. If your credit card company is going to work with you, and you have all the documentation they need, such as a printout of the 100% money back guarantee, you don't need to deal with her at all.
Glad everything worked out for you! If you feel comfortable about it, you can post the website or program's name here, so people here in the future don't face the same problems that you have had...