If an average person feels threaten then it would be a crime.
Was she saying this to the children?
She basically said that I spent a fortune on my house, and I don't want you or your type coming from your areas to play in our playgrounds and infest our environment. I find your type disgusting, and all you do is endlessly breed like insects. It's bad enough what you've done to your own communities - don't destroy our property values by doing the same to our neighborhoods where we invested a lot of money to get a pleasant and serene environment.
She didn't have any actual rights to the area or to be telling the children to leave. There was zero basis for her to do that (it was a public playground). I don't hear her threatening any harm. There were certainly racist/hateful components to her telling them to leave, which she was pretty open about. Is there any legal issue with what she did?