Hi! And welcome to Ageless.
I wish my "problem" was that I was "only" attracted to people 6 years apart from me. I was in my mid 30s and seeking women double digits younger than me.
I think your bigger problem than age is this "eternal friendship" type of relationship you have with the girl. It's very hard to go from being like a brother, or a pal to "hang around" with, to something more than that. I had a friend like that in college who was only 3 years younger. The only thing I would say is to keep building the friendship and enjoy what you do have with her. If and when the time is right you both will realize that there is something more than friendship. In the meantime I would stay open to other opportunities.
Like Abraham Lincoln once said, "You can't believe everything you read on the Internet."