I've been married for 21 years and in love with the same woman for 26 but love of that kind has to be trustworthy and reciprocal. You are about to enter into a decision that is supposed to be binding for life. So, there is a couple of things to look at here:
1.) If after the length of your current relationship she is still going through your e-mails, texts, and phone and you are still visiting sites like MySpace, that as far as I am concerned is nothing more than glorified net hook up site, and complimenting women in a sexual way, are either of you really ready for marriage?
2.) Considering her insecurity, and that's what it is if she is spying on you, and your fear of upsetting her, you're closet smoking and alcohol craziness when not with her, are you even right for each other never mind being married to each other?
Nothing anyone here says will help you to find answers to those questions. Only she and you know the answers to these questions and they are questions you both need to address not just you.
Marriage and relationships are about four main things, love, trust, understanding, and sacrifice. Without these things coming from both ends of the relationship, the relationship is doomed to fail.
Do you love her and does she love you?
Do you trust her and does she trust you?
Do you understand her and accept her for who she is and not what she can become? Does she feel the same way?
Will you sacrifice certain aspects of your life so that the relationship will last? Will she?
If any of the answers to the following questions are "no", Jsaad, my friend, there's a problem and you both need to address them.
Right now there is a tremendous amount of emotion happening that needs to stop before you two can talk. Let it abate. Let her sleep over her girlfriend's house. Time to cool off is good.
Then you two need to talk and address certain things. Love is obviously there but understanding sacrifice and acceptance need work. Let her know everything about everything. Not just this incident but about the smoking and some of the other things she seems to be trying to get you to change. Let her know that there needs to be some sacrifice and acceptance and understanding on her end too.
And if you two are truly committed to each other and can't work it out alone, seek professional counceling.