Unsure of how to deal with a problem customer

Apologies if this is not something that belongs here so feel free to remove if that is the case. I wanted to share an experience that I've been dealing with over the past week regarding a problem customer and a resulting horrible Google Review. Apologies in advance for the long rant..

Last week, we spent six days at a job site conducting some home construction services that were previously quoted and accepted by the customer. This job was nothing out of the ordinary, and normally would take our team about two days to complete. We spent a total of 6 days on this job site due to a difficult customer who was interfering with our staff on site by wanting to be involved with everything they were doing (at one point, she was even standing over their shoulder with a measuring tape and demanding that they explain everything they were doing along the way). This lead to an extremely uncomfortable work environment for the team, and they kindly asked for some space so that they could work safely and efficiently, but would be happy to answer any of her questions if she had major concerns.

The customer then began to complain over minor discrepancies in the quote (of which which she agreed to and signed off on prior to any work starting), stating that we used fewer materials than what was on the quote. For context, the total for this job was roughly $40,000, and the items that she was complaining about totalled maybe $40-50 dollars. Meanwhile, we ended up spending about 30 hours more than what was quoted to her, at no additional charge, so we told her that if she would like us to take the $50 of materials that we did not use off of her invoice, then we would also have to add all of the additional man hours to it as well which would be thousands of dollars.

She then began demanding that we do some work in her garage as well, which was not quoted at all and was completely out of the scope of work that was quoted, so we declined. She did not like this one bit, and began pretending that we had promised to do work in her garage for her and began calling us liars.

She still has not paid the outstanding bill, and recently took to our Google reviews to bad mouth our company, stating that we called her a liar and that we were extremely rude to her, our quality of work was terrible, and she even bad-mouthed some of our employees by name. This is frustrating, because as any business owners know, a horrible review on Google can cause serious damage to your reputation. I am not sure how to respond to this review – on one hand, I'd like to politely tell her that we appreciate her feedback and apologize for her poor experience, but provide context/our side of the story to anyone who may be reading, but that is a fine line to walk as we do not want to appear combative. On the other hand, it feels like one of those situations where you should just ignore it and expect that anyone reading it will hopefully understand that this is just a problem customer. I'm not really sure what to do, but the situation is very frustrating.