to be honest.. you like computers, it's a hobby for you, almost a passion.
So she has to be able to live with that. It's not like you are telling her to quit all her hobbies. (at least I hope you are not)
I'd just put the laptop somewhere and not touch it for 1 month, just to show her that you can live without it and you can adabt to living without spending so much time on it. Give her the battery or something if you want to, just to make sure she knows you are not using it.
But in the end it's your choise, but in my opinion your girlfriend needs to respect you enough to let you do what you want to do, even if it takes a small amount of time that you could be spending together. And of course this works both ways, you need to do the same.