Watched a film a few months back, and I really got into it, but didn't get to see the ending. I'm not sure if it's very famous, but here goes...

Ok, from what I can remember it's about this woman who's a hillbilly, and she's pregnant and leaves the trailer park with her dead beat boyfriend. On the highway, they stop at a supermarket, and he leaves her stranded. So she starts living in the supermarket, until she goes into labour and this man finds her and takes her to hospital and she becomes famous as the "K-Mart mother" (i think). The nice man takes her in, and he lives with his sister who helps look after the name (whom they name Americus because it's a big strong name) until there is a huge twister and the man gets killed and the girl inherits all his money.
But then the story skips to her boyfriend, who's starting a singing career, and I haven't seen the rest!