I also see nothing wrong with what your daughter's opponent did. Juniors often have a tendency to 'play fast' and are coached to slow it down in between points. Walk to the back fence/tarp between every point or count to 10. Mentally reset before the next point.
Even if there were an official there, good luck getting them to do anything about it. In all of my years of playing competitive tennis I have never seen a penalty issued for taking too much time in between points. The most I've seen is a verbal warning (more like 'hurry it up, please') if taking too much time during changeovers, but never in between points.
I'll give the opponent the benefit of the doubt that she as just gathering herself and it's not gamesmanship, but gamesmanship does exist with more experienced tournament players. If that's the case, experience teaches you how to speed up or slow down play to mess with your opponent, but experience also teaches you how to not let stuff like that bother you.