There are two things here that spring to mind. One is, as twinjocks suggests, that she may just be trying to unwind by ranting. As we all do, not necessarily looking for, or wanting, solutions.
The other is the very specific situation of her aiming at a career in performing arts. I have a dd a little bit older who is now at grown-up drama school, so have some experience of this situation. Imo you are right in making this connection and in seeing it as something absolutely essential to get right if she is to survive where she is and continue along this path. Where I think you are going wrong, perhaps, is in phrasing it negatively: we can't support you if you don't manage X. Could it be turned round the other way instead: yes, these are situations which you will find yourself in if you continue in performing arts so let's see about getting an arsenal of techniques together for dealing with it? If you can master X it will really improve your chances for the future.
The first is the recognition that everybody is under stress and worrying about their own adequacy in this kind of place, so people are going to say things they don't necessarily mean. Accepting that it probably isn't about you but about their own inner tension is a good first step.
Secondly, that the most essential part of being an actor is being able to take direction, which to her is going to sound like criticism. That it is very likely that when she comes to audition the panel will say something that sounds like criticism to her in order to see how she responds. That taking that as a learning opportunity is a trick that can be learnt; you just need to keep practising.
When my dd was doing her mock audition, the teacher said to her "What would you say if I were to tell you that you have absolutely no talent and that I think you should be looking at some different career?" It wasn't that he meant it: he just wanted to see if she could stand up under pressure. (She came back with "Thank you. I would say that of course I respect your opinion, but all the same this is something I do really want and I'm going to try to see if I can".)
Thirdly, that performing arts is about learning to get on as a group and that that is what you will be judged on in audition (they observe you from the moment you enter the building- if you don't interact pleasantly with reception staff or other interviewees they won't consider you; group exercises are almost always part of the audition process), Again, it's something that you can learn but it gets easier with practice. Every time you turn a difficult group situation into something positive, by refusing to rise to any baits and by focusing on the work, you are practising for the future, just as much as if you were doing stretching exercise or reciting iambic pentameters.
Thirdly, that relaxation techniques can help enormously here and she should get used to doing them every day, whether she feels she needs them or not. You can find them online.
So basically what you are already thinking - just phrased in a positive way.