Personally, I think that working for "different clients everyday" makes her an Independent Contractor. It seems like randomly scheduled events, that she schedules and controls, rather than a regular time setup and controlled by the parents. Yes, it's a bit of a gray area, but from the very brief description she gave, that is how I think it should be classified.
Here is a couple of links from a Canadian Tax Court case that seems to have similar circumstances that was ruled as an Independent Contractor. Yes, it is using the Canadian tax system, but they use a very similar method of classifying Employees versus Independent Contractors.
<a rel="nofollow" target="_blank" href="
http://www.nationalpost.com/babysitter+employee+contractor/4456447/story.html">http://www.nationalpo...>
<a rel="nofollow" target="_blank" href="
https://cases.legal/en/act-ca1-878357.html">https://cases.legal/en/act-ca1-878357.html</a>
