She doesn't want better. She doesn't want to know who has what to offer. She is content, at peace with how things are, she is genuinely happy- but you just keep pushing.
So often people get scared. Scared of what's out there, scared of starting something with someone, scared of commitment, scared of actually feeling.
People tend to see themselves as less than they are. We are our own worst critic. We spend hours analyzing the methods in which we deal with things, analyzing how we cope, how we move forward. We never praise ourselves though. For a fleeting second we acknowledge the good, only to then dwell on the bad.
When we do that we seem to lose sight of the people we've worked so hard to become. We forget the times we let people with fewer groceries step before us in line, forget the words we carefully thought out in an attempt to make someone's day brighter, we forget stopping in the middle of the road to move the turtle, we forget holding the door for strangers, we forget how we always say "please and thank you" and we focus on the rest.
We direct our entire focus on the times we didn't give cash to the man holding cardboard on the side of the road, on the times we lied to avoid leaving the house, on the times we looked the other way when we shouldn't have.
I won't argue with you, there's always room for improvement. But, you are trying and it's okay to give yourself credit for that. It's okay to acknowledge your flaws but it's also important to recognize your potential.
You can't be afraid to let that heart of gold love you because you're scared you aren't worthy of it. Newsflash, if she sees something in you, you are in fact worthy of everything she's willing to give you. Put your pride aside, stop worrying about what people think, what your friends will say, stop worrying you'll miss out on the fun and let her be there for you. Let her remind you how extraordinary you are each and every day because she wants to be that girl for you.
So, please quit telling her she deserves better and let what you have to offer be enough. Stop being so terrified of letting someone else play a part in your happiness. Stop using every minor thing as an excuse before you lose something amazing. Continue to admire the way she's so selflessly independent, the way she knows exactly what she wants. She doesn't deserve anything different and she sure as hell doesn't want it.