My daughter is now almost 18, so I've been through what you're going through. I also do emotional healing work as a profession (in a different way from regular counseling), so I've worked with many other situations like this.
I read Diane D's response and liked it a lot. It points out that when we're thinking clearly we can understand a lot better why other people (including people of other ages and stages of development) do what they do. You need to find the place in you that can understand and empathize with her reasons, including the fact that she may have some anger (mostly at her Mom, maybe her Dad and you, too) and is trying to assert her independence as an adolescent.
As you've seen, when she senses you're really coming from love and acceptance of her, she opens up and talks about some of her feelings. So I'd work on exploring what in you is being triggered by her behavior. If you can love, accept and heal yourself (the child and adolescent parts within you) you'll be able to be present with her feelings, reactions and MISTAKES (which is probably what the computer thing was) without getting upset yourself, in a more consistent way.
And in the meantime I'd allow her to make as many of her own choices as possible (anything that doesn't directly affect her safety) and live with the full consequences of them. That's how we learn! The key is not to bring your own emotions into the process of telling/delivering the consequences. I wish you all the best; I know it's not easy!