Is there any way to tell her this? like the last sentence of your post is really good, it's straightforward, lets her know how you feel, but doesn't sound mean either...I don't know if you can or not, though, and how open you feel you can be.

But I think it would help her learn, and if anything, she should appreciate it because she IS learning and should expect to make mistakes, I am just sorry those mistakes are happening to you...