Buster, I think society still has a long way to go in our journey towards full inclusion. I think the lack of acceptance is multi-faceted and could stem from any number of issues or even a combination of them.
Lack of exposure to people who have physical disabilities would be one big cause of the issue. The more we see, befriend and work with those who have disabilities, the more normalised it becomes...and therefore, less intimidating. Problem is, lack of exposure causes people to be nervous...and their nervousness would stop inclusion...it's a never ending circle.
I think another issue would be her lack of confidence. Some people are so caught up in what others think that they'd be all worried about "what will people think if they see me with someone who looks like X?"
You sound like a great guy. Your ideal girlfriend will be one who doesn't give a toss about what others think. She will be someone who sees past your disability and sees what you have to offer. Hang in there and keep trying.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.