What do I do about this?

I've got a friend who I'm not that close 2 but am still friends with, I've tried being closer but she refuses to. She keeps fainting and she's got this big secret whom shes told everyone in our friendship grp but me, I don't know y. and now there all talking about it and I'm not allowed to know cos its "personal stuff" and I mean I know its selfish but I just can't help feeling left out and unhappy. I'm a good lisner so i dno y she dsnt tell me i even straight out askd her. then they all askd me whether i "knew" so i paniked and sed yh and she din tell me anything and now well its all a BIG mess nd I dno what to do??