I feel it was a little over the top, but it was the fact that the parents were filming it, that actually meant that the staff member had to do a particularly thorough and by the book job.
The upset of this child was, in my view, added to by the parents stance and the conversations held prior to the search were not filmed.
The security staff member was just doing what the US Government have asked her to do. It is, in-fact, a well known fact that smugglers often use their children and although this child was unlikely to be in this category, that is maybe the reason that children are included in the search processes, in the USA and probably many other countries.