Everyone has standards as to what they find attractive. There are instances, that at first you might not think that person is entirely attractive, but over time they become better looking as you look past their flaws and get to know them a bit better. I would say you must really like her, possibly have the potential to love her if it works out.
It's probably the same reason how some people like bull dogs or pugs; they're not aesthetically pleasing, but they're so ugly they become cute. If you like her and she likes you, don't worry about what other people think. They don't live your life; you do.