Ex-sister in law posting fake reviews of my business online how do i get her to stop?

My brother recently 3 months ago moved into my home, he has been divorced for 7 years. My ex sister in law has been attempting to contact both me and my husband privately which we ignored and in retaliation she recently began posting defaming comments of myself and my business online affecting my ability for future employment and ability to make an income and possibly affect my current employment. because of these comments I am considering shutting down my business all together which is in 3 years in business. I have been unable to sleep because of the stress and i cannot afford to hire an attorney for 50k that i have been quoted. how can I get her to take down the messages and leave me and my husband alone affordably?