I don't hear your T saying that you were "wrong" to send an email that was true to your feelings. Rather, I think she is attempting to get you to both understand where your feelings come from and see your effect on other people.

And she is "putting up with" you. She didn't send you to another therapist because you sent this email. She gave you her honest reaction of frustration with you. And that is her job among many others-- not to be your punching bag-- but to let you know how your behavior and words affect her. That is extremely therapeutic, as you will have ZERO success with healthy relationships in the real world unless you really GET this.

But your feelings about her frustration would probably be great for you to explore in T, along with your sense that she is somehow being unfair to you.