I agree that your t cares about you and is looking out for you by telling your mom. I also would not be able to trust her after this because she didn't tell you she was going to do it and especially if she emailed after the first session. its because you are under age that t had to tell your mom but I don't think email is the best way to do this.
I imagine you are angry at your t for betraying you but she has to, its her job.
Sorry you are feeling like you don't want to be here, you have your whole life a head of you, things are always changing nothing stays the same so your circumstances will change and get better, it justs takes time and some self TLC