Do you and your girlfriend both work? What is it about her that makes them say she is lazy and not for you?
Personally, if I didn't like them feeling like they could run my life, then I'd stop accepting the money. They might be trying to make you feel obligated by giving it to you. You don't have to choose, tell your mother that you love her and you love your girlfriend. Who knows, you may come home one evening married. How would she like that?
I finally reached a point where I realized that certain people (like my mother) cannot be pleased. So I treat her just as I would have her treat me, and when she oversteps boundaries, I explain to her that because of her behavior, I will not be speaking to her for a few days.
Sounds like I'm dealing with a toddler, doesn't it? But honestly... my mother is infantile in many ways.