I don't know how to deal with my friend Options

[funky_munky]

Since I've known my friend since grade 5, I trust her with a lot of stuff (including some of my family problems).
Once, I told her something that has to do with my brother and I told her specifically not to tell anyone and she promised she wont. Then, when we were sitting in a group just having a chat and a similar topic is brought up, my friend laughs about the problem I told her like it was some funny joke.
I pulled her aside and told her to stop it and she goes "What? Its true."
What I want her to know is that, yeah its true but have you ever consider my feelings? I try to tell her that but she doesn't get it.
Then when I mention the times she's said it, she turns hostile.
Everytime I tell her something about her that bothers me, she immediatly denies it without letting me finish and turns really unfriendly.
Like, she would started questioning me "When did I do that?"

Help me out here, I can't think of a way to get her to understand that what she's doing is annoying and rude.
I've told her to her face but that just led to an argument and my other friend told me not to be so blunt but... I dunno... I need some advice.

**sorry if this is confusing