Sold Made to Measure goods-not been paid balance

[frankel]

Hello,I sold made to measure blinds to a customer who paid a deposit and after fitting of the blinds refuses to pay the balance,claiming they don't cover the windows completely. During the survey I pointed out the limitations of installing any blinds, and she specifically requested these types.She's arguing that they don't give 100% coverage or blocking out.The balance was doe on fitting,when she refused to pay; she told me not to contact her again when I sent a text message asking for the payment few days later.I sent an invoice 10 days later and got no response. One month after the invoice,I've sent her a Letter before Action and she sent an email the next day in which she's states certain parts of the blinds are different colour, which are patently untrue,and which I can easily disprove( These would have been easily visible at time of fitting but she did not mention this at the time).However, as the goods are in her possession she can do anything to them claiming that's how they were when fitted. The blinds are the colour she ordered, they work as they are supposed to,the controls are on the sides she ordered. However, in her email she states they're unfit for purpose and demands a refund and wants to return the blinds.
As I said I've sent her a LBA giving 7 days to pay the balance.Should I respond to her email, or ignore it and start a s claim?
Thanks