I don't know what to do... please help?

Hi everyone, so I have been with my girl friend for 11 years, and we decided to finish school before we got married. Now we are both done and we want to get married, but there is an issue. Her mom lost her job for about 5 years ago and is still receiving her unemployment checks. My girlfriend has a dilemma because she feels like she needs to help her mom out, with around $1000 per month. The problem is that I can't afford it neither can she, so we would have to struggle to make that $1000 monthly payment to her mom. My argument was to not help the mom, and save and stabilize our life before we can help others, she thinks I am selfish and says that she can't just leave her mom and because of that can't marry me... any good advise? we are both in our early 30's, none of us have kids or ever been married before.