Glad your parents are out, so you still have your family when you cut free as well. Your girlfriend? Well she has basically told you that she wants to stay, let her stay and move on even with a sad heart. It will be much better for you both in the long run than all the misery that will surely come leading a double life and feeling trapped with someone you love but who does not trust you or share their true feelings with you.
You are young, wish I was your age when I woke up, but on hindsight if it had been my husband back then telling me he was finished with the Jw's, then I think I would have dug my feet in and become even more "spiritual". It was a great defining moment for our marriage when it was me that made the decision not to go to meetings anymore, my husband who was an elder, took less than two weeks to decide to join me in leaving.