What can I do to get the money one of my customers owes me?

I sell Herbalife products, one of my customers decide to return her products and get her money back. We have a 30 day return policy. I returned her the complete money in cash from my own pocket and she returned me the used products. What she didn't mention was that she declined her transaction she made to purchase the products and she got that money back. So she got the $185.68 in cash and $185.68 from the Herbalife company. Two months later the company tells me there was a declined transaction and I have to pay back and if I don't my Herbalife membership will be blocked from selling any more products. So I tell my customer what happened and she said she had no clue of what happened. I showed her the letter from the company saying the balance was $185.68 plus a charge back fee of $25. She paid me $100 two weeks later and said she was going to pay me in the beginning of the year and it's already a whole month later and I haven't received any no more payments. She still owes me $110.68