You can send a request to Google with evidence but they usually won't investigate the situation to determine what is true or false. My recommendation is that you post a response that is professional and factual to defend yourself. If yours is a good and hers is full of insults and ranting, readers will recognize the difference and assume she's a nut.
Here's an example from one of my negative reviews:
I youtubed this question and I saw video explaining that if you get your friends/family to find the bad review and have them report it for being inaccurate or dishonest (whatever the truth is) and if you get over 5 people (more is better) to do it Google may review it. The youtube comments said it worked.