How do I keep my girlfriend interested in me & her to not start talking to guys on the side?

[Coyote]

First of all, you need to set parameters for yourself, and make sure your girlfriend knows what they are. What kind of behavior is unacceptable to you? What do you consider a "deal-breaker?" She won't know how to stay true to you unless you define what that means.

Second, you need to be prepared to reciprocate in kind. The parameters you set HAVE to be parameters she can expect of you as well. Don't be a hypocrite.

Third...you MADE her delete her Facebook? The more you try to control her like that, the more she's going to defy you. You don't have any right to encroach upon her as an individual like that. You need to back off and afford her a little trust. If you don't feel you can do that, or you feel the trust you afford her is being violated, you should probably both acknowledge this and break up.