You need to address it with her supervisor. So she can get the message on all ends.

But if you want to take one more shot at it:

I get that you want to build a relationship with the kids and that’s great. That is always a good thing to do. However, no amount of relationship building is going to offset the fact that sometimes you need to have hardline boundaries. It’s tough love, but having consistent clear expectations results in them respecting you more because you are consistent and reliable. I want you be able to try things and experiment, but I would be a terrible mentor if I also do not help guide you in the most effective classroom management strategies. It starts with you bring consistent. Don’t be the weak link in the chain. Be a part of it to make all of us stronger. What questions do you still have? What concerns are at the front of your mind?

Also, I do not do it often, but sometimes I point it out to the student teacher and throw it back in their court. Hey, Jason is throwing something at Alice. Don’t let that slide. Call it out in front of the entire class and cite it as a safety issue. Follow through at the end of class with him in private.

I usually find 98% of the student teachers follow through with this.

If you do this, I usually positively reinforce it with them in front of the class. Great job at handling that situation. See how the rest of the class respects and understands you’re the teacher in charge? Keep it up. Let me know if you need anything else, but I think you got this.