You're making this way more complicated than it needs to be. Any parent understands the need to set bounderies and limitations for their children. The reverse is also true. Kids need to set bounderies and limitations for their parents as well. Many times, the parents won't respect it and won't listen, but that doesn't change that fact that you need to do it.
Your mom has to be aware that she's crossed a line. Actually, she already IS aware of it. She hid the diary, didn't she? Do you hide things that wouldn't cause you any problems or make other people upset? She already knows how pissed off and betrayed you'd feel if you knew she had read that diary.
You need to approach this carefully, however. What your mom did was VERY wrong and I don't want to stick up for her, BUT I do want you to take some time to try to understand why she did it and how she feels. It doesn't justify her actions, but it might help you in dealing with her if you understand her motivations.
One of the major problems in the Youth Rights movement is that it's a bunch of kids who've never BEEN in the role of a parental figure, so they don't understand the complex and confusing emotions of being a parent. I see this all the time. Kids think their parents are "evil" and "just being controlling assholes" when all that's really happening is that their parents are afraid and hurt deep down inside.
As kids get older and become their own independant people, they share less and less with their parents. This is the normal and natural course of a child's development and intellectually most parents understand that. Doesn't make it any easier for them. Try to imagine how you would feel if the person you loved most in the world was slowly excluding you from their life. Not only that, but you know intellectually that it's normal for them to do it and that YOU aren't even "supposed" to feel hurt by it. Everyone expects parents to just "let go" when the time is right. For the most part, parents do, but they keep inside exactly how they feel about it.
Your mom didn't want to be nosy and invasive. She didn't want to violate your privacy. All she really *wanted* and *intended* was to feel closer to you; to know the things that she wishes you'd tell her but that she knows you won't. For all the talk of how young children are so dependant on their parents, people gloss over the fact that parents are equally dependant on their children too. You get used to knowing all this little person's hopes and fears. They share all of themselves with you, until they're old enough for society to teach them that they're not supposed to. And the parent is left feeling cast out and in the cold.
Oh yes, I know this feeling. I talked about Meg in the last Sniper Radio. It hurts to know there are so many things she doesn't tell me. Not because she's keeping secrets from me, but because it feels like she doesn't trust me enough to share those things. Now, intellectually, I know that's completely fucking retarded. She's grooming her own individuality and part of that is having her own life seperate from those that have authority over her (and whether I like it or not, I fit into that category). Still, logic and feelings do not play well together and no matter what I may know in my reasoning mind, I still *feel* untrusted, unwanted, and unloved by this kid who used to trust, want, and love me SO much. That change sneaks right up on a person. It was very sudden and very shocking for it to happen.
So if I came across Meg's diary that she'd thrown away, would I read it? I like to think that I'm above all that and wouldn't let my emotions control my actions (as I'm always admonishing others). If I'm being perfectly honest here, I can only answer that I don't know if I'd read it or not. If I immediately said "Nope, no, fucking no! Not gonna do it!" and threw it away, ok. But if I allowed myself to think and dwell on it... yeah, I might read it. Jeez, no wonder she doesn't trust me, right? LOL! The point is, I wouldn't be doing it to invade her privacy (though that IS the end result) and I wouldn't be doing it to intentionally disrespect her (though, again, that IS the end result). I'd be doing it out of the rediculous emotional need to feel close to her again; to feel like I'm not on the outside of her life, looking in.
This is what I want you to understand about your mom before you go all batshit fucking pissed off on her. Yes, you DO need to confront her about it, but you also need to remember that she did it out of hurt feelings and desperation to see inside your life. Lashing out at her in anger will only hurt her more and reinforce the emotions that caused her to do this in the first place. It should go something like this.
"So, mom.... I was looking for a game of mine that I thought had gotten mixed up with dad's DVDs. I didn't mean to snoop, but... *hold up diary* I found this anyway. I'm not mad or anything and I understand why you read it, but I need you to know that this is unacceptable and something like this shouldn't ever happen again. Those are my private thoughts and feelings and I'm allowed to have those without you knowing them etc etc blah blah blah."
You get the picture. Be sensitive about it, even though YOU are the one who was wronged here. I know that's hard as hell to do, but if you're a dick about it (like you really have every right to be) you're only going to make it worse and pretty much guarantee that shit like this will happen again. Be diplomatic and play on the guilt that she most certainly already feels for having read it. If you get angry, you'll provoke defensive anger from her and that, in her mind, will translate into suspicion. "What's he REALLY so angry about? What's he got to hide from his mother?!" In truth, what you've got to hide from your mother are exactly the sorts of things that any normal and sane person hides from their mother. You're hiding "omg Jenny is SO fucking hot, I'd like to ram my cock up her ass!" but if she gets paranoid she'll be thinking things more like "omg this fucking heroin is DA SHIT MAN! I gotsta shoot me sum MOAR!"
Hope that helps, but you'll probably just ignore it and pretend you never found the diary, you pussy.
All My Hate,