How long is it since you saw this girl in person? As you said, everyone changes, so she may have changed too. I suggest that you try and arrange to meet up in a non-threatening situation, such as a reunion with a group of mutual friends. That way you can see if you still really do like her, and she will be able to see that you have matured. After you make that contact, you will find it much easier to continue to woo her in chats. If you can't meet up with her, perhaps you could send her a chat saying something like, "Hey, remember me? I was pretty weird back then, I know! How are you?" and see if she responds. This way you're telling her that you are aware that you might have not been attractive to her then, but you have changed. It could open up the lines of communication.