Goes around damaging business's reputations online for small petty things

I'm the owner of a small business, which took me years to build, and Conchita Mendes Teaching harassed my business by phoning our Whatsapp number continually (about 15 times) in one day. It clearly states that this number is only for Whatsapp and after not getting her way, she gave a 1-Star Google Review Rating, damaging our business image online. Conchita Mendes Teaching did not even try or consider sending a Whatsapp message or email. She could have sent a whatsapp message or email and would have received a reply swiftly. We sent her a whatsapp about this but she ignored the message. From what we can see online, we are just one of many businesses that received 1-Star google reviews from her for something very small.