As just about everyone else said, it's just part of life at a big barn. We have tons of people hanging out on the judges stand, riding in the rings, walking around, etc (rule is to stay out of the way of the person lessoning) and sometimes lessons get watched. In fact, I actually think it's a good idea to watch other peoples lessons, you learn a lot by watching. Discuss it with your instructor if you want to, but there's probably nothing she can do about it.
There are also times when people interrupt me when I"m teaching. I don't let people have a conversation with me, but if someone comes up to me and asks where the fly spray is I'll tell them. I also don't answer my phone during a lesson, but I will look at a text during a walk break if it's from someone lessoning that day, simply bc I need to know if they are cancelling last minute or if they're having trouble in the barn getting ready. I feel like I can do a decent job teaching and still do those things. If she is standing around talking to people ignoring you? That's a problem.