If you're just friends who are sweet on each other, and keep it that way, nothing is wrong. However, 13yo girls are easily flattered by your 'age and experience.' It's up to you to not abuse your leverage. Do NOT make it sexual. If it is true love, be patient. If it isn't, you won't hurt an innocent girl.
You're both jailbait at this point, but if you keep your relationship above board, and spend a lot of time with her parents so they get to know you , it could be okay. Nothing lasts at your ages anyway.