1.)To be honest this whole thing doesn't sound legit, not to call your posting of it into question.
But as of now we don't have any solid facts of the person who supposedly sent the letter. In every story I can find about this, she mentions more & more how she felt marginalized because she was a minority, not to mention being a woman. Its the same kind of talk we here from woman saying how downtrodden they are through a buzzfeed post.
2.) It also doesn't seem like something a person living in the 21st century would do. Even today we have people calling political figures on their home lines just talking **** en mass, this honestly seems like something an emo hipster would do. I can see someone sending a hand written letter as being more credible then this.
3.) There is also the fact that this writer basically marks themselves as a Trump supporter, why?
4.) If you want to make a statement, just say what you are going to say, and be done with it. This just screams "FAKE" every time I read it. Like all of those so called hate crimes that started to spring up after the election, that were being perpetrated by Trump supporters. Only for a week to pass, and a vastly mounting number of them were proved to be wrong.
Until we have more information about the writer of this letter, I withhold judgment on this actually being a Trump supporter. Either she is duping the news, or someone is duping her in all of this.