Should I stay or shoud I go?

I have been with this young lady for almost 4 years now, I watch her children every day while she is at work and in the mornings while their mother sleeps. The reason I can do this is we were involved in a head on collision to which I laid my life on the line to save hers. If I did not turn toward the person who hit us, she would have been killed. Still her family persists in criticizing her about who I am even though I have helped them out quite a bit. The only person that seems to give me any respect is her father. They make her cry because they leave her and her children out of family events, presumably because of me. I have never seen the likes of how these people treat their own. I wonder if me not being here would make my other half better off, oh and yes, I do pay over 50% of the bills and have paid for her children's school clothing.