My opinion is if you have already spent a lot of time in the last few weeks, and then you expect to spend the Christmas holidays playing even more, then I can understand her.
Although I disagree with fletchdad when he says poker is either an income or a hobby, it is true that the time investment can be huge.
The christmas holidays are indeed the perfect time to do this, but you can't do it everyday if you have a girlfriend and kids.
The grinding of a budding startup
bankroll will require more time and bring in less money.
You might want to take your time and keep grinding in SNGs and MTTs occasionally until your stash is secure enough to switch to ring games, or take the chance to inject it with immediate cash and jump to ring games immediately.
Poker is enticing. When you win you want to spend more time playing, and when you lose you want to spend more time playing. Poker discipline also means factoring in whatever is also present in your life outside of it.
In the end, if you spent several hours everyday of the last weeks playing, and then expect your girlfriend to smoothly accept your will to spend even more time playing the Christmas holidays off, then you will be disappointed.
Besides, the time when I enjoy playing poker the most is when my GF is asleep or out of town to her parents, then I'm alone at home and I can truly focus and that's when I play my best.
Poker, to me, is truly one of the most rewarding forms of "me time". I've made money off of it and it contributed to restoring my '65 Impala SS, so it's a hobby yes, but a hobby that made another one possible with no financial strains and to me, poker has been a hobby, a source of income, and also an enabler of greater things.
Granted, I was single when I played the most and made the most money, but nowadays, I accept my situation and I play only when I can and when I know I'll be at my best.
If you know your girlfriend will be irate that you spend so much time at the tables on Christmas time, your head will not be clear and you will not play your best game anyway.