Maybe she senses how much you love your Bonnie and therefore loves it herself. Or perhaps the Bonnie simply represents the quintessential motorcycle.
To fake-philosophize further, I agree that beauty truly is in the eye of the beholder. I have liked pairs of shoes or shirts that I know others certainly didn't appreciate. But then again there are people, art, clothes etc., that everyone agrees are beautiful. And I think the Bonnie is similar in the sense that its classic lines are are appealing to everyone. At least what I think based on all the looks, driving next to for miles, and comments etc.