That was very bad of her. She didn't even care about the sacrifices made by the owner to plant and nuture those flowers and she stepped it take what dies not belong to her.
If you decide to take necessary actions now to sue her, she will tag you as wicked forgetting what she did was terrible. 

Imagine how some people were even in defence of her that Posting her pic violate privacy. Why did she stepped beyond her own boundaries and take what doesn't belong to her? Does that nor violent the law too? And how then do we intend to catch her if her pictures were not shared?

Putting "YOU ARE ON CCTV" is a good idea but there are those who will find a way to evade that upon seeing the sign board.