For your sake, you need to get out of the relationship.
She can't love you if she can't love herself enough to take care of herself. When I got married and had children, I took better care of myself because my family needed me. I would not want them to suffer because I was reckless and got injured/crippled/killed because of it.
I know that 2 years seems like a long time and that you think your gf is the love of your life, but 2 years is a relatively short time for a relationship. A 2 year relationship is only long enough to get over infatuation and start getting to really know a person. I would not commit myself to perhaps years of drama/suffering/insanity based on a 2 year relationship.
If you tell her family, I think it would be the responsible thing to do because they have known her for her entire life and deserve to know. If you don't say anything, I would think her family would eventually figure out that something was wrong. But by the time they put it all together, things may have gotten really bad. Either way, it does not matter how much she needs help if she does not want help.