Interesting question. You have several civil causes of action that you can and should bring against this person. First, you can sue them from breach of contract relative to walking out on the lease. You are entitled to the remainder of what was owed on the lease and arguably reasonable damages on top of that as well.
You also have a cause of action for what is called tortuous interference with business. Their actions in developing a client base under the business good will of your business and then in turn leaving - coupled with their post on YELP, is a prime cause of action for tortuous interference with business. You will need to show their actions either have or are likely to cause your business harm, that they planned this out and that you have or will be damaged.
You also have a viable cause of action to sue them on relative to civil fraud based on the post on YELP that your business has moved. You will need to show that they knowingly made a statement that they either knew or should have known to be false and that it was intended to defraud potential customers and consumers, and you will need to show a likelihood of damages.
You stand to gain not only reasonable damages on all fronts, but you should also be able to get attorney fees and even punitive damages under the circumstances. I would recommend hiring a local attorney to represent you. You can go at it alone, but an attorney will be your best option that is local to your court system in the county in which you live.
Let me know if you have any other questions or comments.
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Best wishes going forward!