I can't even see myself falling for this kind of crappy scene. I don't see a good reason why your girlfriend would have to tell you to stop what you like doing just to make her happy. This is highly rediculous and there should be a reason for that. Many things is attached if she would be ready to bear and pay all my bills. I know there are some persons that cannot do without betting in a week. Gambling gives some persons joy especially if they are making consistent money from it.
The context your painting in this argument if you could allow me to call it that, although there is no rules to your reaction and how you choose to respond is entirely up to you but, in the event that your loosing so much and it has raised concerns and in this case, the concern of your girlfriend most of all and a few members to the family, a little step backward won't be exactly taking orders from your girlfriend.
I understand what it means to have a woman make you do a task or something but, it shouldn't be about that in this case, it should be about well being. You've got to evaluate it and see if it's good then, you could choose to work on yourself.