"" nobody ever proposed to me""
Ugh... I gotta say I feel for you man, that is rough. In my experience, these little off-hand type comments are much more indicative of a person's true feelings than the ones that happen during conversation.
One minute its "eh, later is fine" and then its "nobody ever did that for me..." wow
Do you think she would say yes? Do you think its what she wants? You could try feeling her out by going ring shopping next time you are out. Stay away from bridal magazines, as they are just a tool of consumerism, and a fast road to debtsville.
Does she work or hang out with more traditional people? It'd be a shame if she was constantly dealing with those "you have a baby and you aren't married" types. I know that is tough to deal with, so maybe with a ring on her finger, it would help her defend against that.
But as long as you affirm your commitment to her, she may not even care about the ring. I love it when people are enlightened and say "I don't need a token to prove I'm loved".
Best of luck.