What should I do?

Right now, I'm in a situation where in I don't know what to do.
A lot of things had happened and will still happen.
Sometimes, I just don't know how to handle things anymore.
Someone would text me that she's not in a good mood; next thing I know, I'm also not in the good mood.
I know that a secret can ruin everything.
Everything including FRIENDSHIP.
But what can I do?
It's not my secret, but now I'm hiding it also.
Someone asked me not to tell anyone about it.
I don't want to lie by saying such things as "I don't know," but I really don't think I'm the right
person to tell them.
I don't have the right to spill things out.
I still don't get the reason why I can't say it, but I'm sure that it can start another conflict between us.
I just hope that if ever they would know this, they would understand why we have to do hide it.
Now, she's mad.
I can't blame her for that.
I don't want to break her trust.
So, I'm still not saying it.
Unless she gives me permission.
I just don't know maybe at this time, they already know.
I know that no secret can't be revealed.
Please understand.
I don't want our friendship to be broken because of a secret.
I know we promised that we should not hide any secret from each other, but please understand that some secrets are really meant to be hidden.
I know the right time will come and you'll know about this.
I know it's hard for you because you don't it, but it's harder for me.

I'm really sorry.
I hope you would understand me.