Ok, if someone tells you that something happened when they were younger that:

1. No one else knew about until about a month ago.
   
2. It's a pretty big secret. Even her parents don't know.
   
3. Recently she got a boyfriend and she had to tell him in order to answer an important question he asked.
   
4. He tried to guess a lot of horrible things before she told him, and none of them were right. When she did tell him he was completely in shock..
   
5. He wanted her to tell her parents, but she didn't want to so he convinced her to tell her sister...
   
6. Apparently it's really hard to figure out. At first I thought some sort of abuse but if it's that hard to figure out...?
   
7. When she told her sister, her sister was sympathetic and said she wanted to talk to her about it..
   

She wants me to know but can't say it, and said it would be easier if I guessed it. It's so bad that she can't bring herself to say it again. =/
Any ideas?

I'm usually good at guessing things I guess. =/
She doesn't want to so I won't force her to..plus she know it's not a game, and since she told her sister I guess she'll have someone to talk to about it if any serious actions need to be taken cuz of it..whatever 'it' is..I was just wondering if anyone had any ideas as to what the big 'secret' could be. I rather be able to guess it than make her say it.

Thats the first thing that comes to mind for me too. =/
Besides if it wasn't something sexual..why would her boyfriend need to know? Although she's only 16, and she's a strong Christian too so she wouldn't get sexually active with him anytime soon soo..
If it's that though, why would she say it's really hard to figure out? Being sexually abused is unfortunately a bit common..