I can see why you would feel shorted. In the other hand, if your daughter enjoys the lessons & is making good progress, those interruptions are no biggie. The price seems reasonable enough, so my main concern would be whether the pop ins are distracting your daughter and/or the teacher.
As far as shorting the following student when a lesson runs over, it too seems odd, but maybe it all evens out in the long run. If it frequently impacts you daughter's lesson, that would be an issue.
Confrontaion is a skill that you can learn, btw.