Difficult work situation - can anyone offer advice?

I've anxiety, and I'm also Autistic.

My employers do not know I'm Autistic or that I've anxiety.

Technically it's not work, but a voluntary role (I need to work voluntary jobs for recent work experience and references).

I've had a serious fear of phones for a while but over the last few weeks I've managed to overcome that to work on the phones in this voluntary position, so that's a plus...but I'd still like off the phones and would rather deal with clients face-to-face.

I'm struggling with face-to-face, not because I can't do it and I'm not anxious about dealing with clients face-to-face but because in order to go forward with this I have to have a trainer sit in with me on a few of my initial appointments with clients.

I feel my trainer is becoming aggitated with me, she's supposed to be shadowing me but instead she's having to take all the clients and I'm just sitting in, she keeps trying to push me and she sits with me between appointments just hanging over me so it's adding to my anxiety.

In situations like this I get stubborn, I've been refusing to even consider taking cases and now I'm just refusing point-blank every time she offers me a case to do myself. I feel she's getting mad at me for wasting her time, I fear they're going to ask me to leave if it continues, but I just can't seem to break out of this because the more she is pushing me into it the more anxious I get and the more I dig my heels in.

I attempted to take one case the first time she shadowed me, but it didn't go well as the client kept talking to my trainer so she took over - I believe this is because the client was older and so is the trainer, although I'm an adult in my 30's I guess it's a generational thing.

My trainers/supervisors seem to think my refusing to do this is because I lack confidence in my abilities.

This is not the case, I think I'll do fine face-to-face, my anxiety is purely due to the idea that they will be there listening-in to me.

I can't tell you exactly why this makes me anxious but I've ALWAYS felt this way, I've been known to rip up important art pieces and even drop out of art in college because I couldn't cope with peope looking at my work while I was working on it. It may be that I dont like criticism (although I don't like praise either!) and not being absolutely perfect, but also I'm independent and just prefer working on my own.

I'm not sure what to do, I'm so worked up if they try to shadow me in face-to-face again - rather than just letting me go back on phones - I may suffer a [autistic] meltdown or freak-out on them and walk out of the job all together. I'm just not sure how the hell to calm down about it and explain that maybe they need to forget about me doing face-to-face for now as I'm not comfortable with this trainer or being listened into - but I still also feel like I'm causing them a lot of drama with this, I'm not really sure how to save face and get back on track here.