Anyone would feel like dying if they got a letter like that from their mother.
You won't like this (sorry). It's not true that getting a letter like that would make anyone feel like dying. I've GOTTEN letters like that from my mother. They made me want to AVOID her like the plague. That's about it.
Here's the deal. First, because my relationship with my mother was atypical at best, this is NOT my best subject. But, as I understand it it's true that parents, best case scenario, want the best for their kids. Unfortunately, they don't always know what that IS. And they see things through their own lens too.
That letter was an attempt, by your mother, to manipulate you. She's using guilt, for one thing, to try to get her way. Her whole attitude isn't healthy and it isn't helpful. Best case? She should appreciate you for who you are, respect you for who you are, and want you to grow and learn, and become the best possible version of yourself. She's wrong when she thinks she gets to decide what that is. YOU get to decide that, if you want to do it.
I'm going to take a wild guess and say it won't matter what you do, she'll never be satisfied. And that's because of her issues, not yours. Your job isn't to live your life for her. Your job is to live your life for YOU, the very best you can.