Welcome Grizz. You can do this...but you have to do it for you. Ultimately your girlfriend will benefit from your quit, but you cannot quit for her, it won't stick. What's the first thing you're going to do when you two get in a big fight, or heaven forbid, you guys break up? Back to banging the can. You have to quit for YOU. The rest of your relationships will sort themselves out.
That being said, you've made a great decision to take your life back today. Each day you commit to your quit, post roll, and keep your promise is another day of freedom that nicotine did not allow you to have. Now you're in control again. The only way you lose that control is to consciously concede that a plant pumped full of poison is stronger than you are. One day at a time. Post your promise. Keep your promise. Repeat.
Proud to quit with you today.