Legal Advice Urgently Needed On A Client Refund Request Issue

I need legal advise on an issue involving a client's refund request. A client paid money for our service to help her set up a business. We spent a lot of money to pay for platforms, software, website hosting, website designing of client's website, online banking software, virtual private servers, affiliate management software, help desk support hosted software, graphic designing of over 100 brochures, design of various PowerPoint presentations, logos, business cards and other stationery on behalf of this client. According to our service terms, we have completely delivered on the services paid for, by this client. And the client acknowledged that she was happy with the resources and everything set up for her business. Plus we continued to offer her ongoing support for her business and also helping to attend to prospects that inquire about her business. There is no question about we having delivered our part of the service agreement between us and the client. The client has acknowledged it, there is abundant indisputable proof of everything we have set up for the client available online for any one to see. Most importantly, we have a business agreement that was signed between the client and us via [login to view URL] . THE PROBLEM About 2 weeks after setting up the client's business and all the resources we spent money on, to set up, the client just sent us an email yesterday asking us for a refund of the money paid for her business set up. Her reason is that she has not made money from the business set up for her, although she has been making effort to market the business. Meanwhile, it is not part of our responsibilities to bring clients to her business. It is her sole responsibility to market her business and to attract the clients that would generate income for her business. I need legal advice on how to handle this issue for two reasons: 1. If I issue a refund, it would not only be absolutely unfair to us, it would be a colossal financial loss to us because we spent almost all the money she paid for her service to set up everything we set up for her. Beside, there is no justification for giving her a refund 2. If I insist on not issuing a refund, she could do a fraudulent credit card charge-back via her bank because she paid for the service using credit card. And getting a charge-back is something I don't want to ever experience because of the reputation I want to continue to maintain with the payment processor that I use to process credit card payments. SOLUTION REQUIRED I am going to explore the option of negotiation with the client, even though she sounded absolute in her email requesting refund. I need advice, solution and proven ideas that would help me not to issue a refund, while ensuring that a credit card chargeback does not happen to my account in any way. If you are an experienced lawyer and knows exactly how to deal with this kind of situation, I'd like you to bid by giving me strong reasons to believe that you know how to deal with this situation and what similar cases you have dealt with for other clients and how it was resolved, and how this could be resolved. If I am impressed with your response and choose to work with you, we are going to be working together for a very long time since every client relationship I enter with all my clients always involve the signing of legal agreement before we start working with any client. I look forward to your bid and detailed response. Thanks for bidding