I need alot of answers why would she do it????

My guy and i have been dating 6 months,and he wrote a letter telling me about how he felt and some other personal things, he wants to be serious. But i am scared .So i confided in a friend it is someone we both know we are all from the same neighborhood, in our 30's. Showed her the letter just fo her opinion to see if she could detect something fishy. She told him i showed it to her!! Now he wasnt upset but he wish i would not have done it he felt like it was an invasion of his privacy. He says tracy "said i saw your letter" loke she was taunting him. Was she wrong?? what good did she think could come of that???????