Is it inapproriate and or haram for me to be friends with a 13 year old girl?

I am 17, and a brother, and I am currently friends with a 13 year old girl (who is also Muslim)......well, I don't know if you'd count us as friends because we rarely see each other......but we hang out whenever we see each other......but I have two problems.....one, she's a namahram, but personally I don't believe there's anything wrong with just being friends, and two, her age.....is it wrong for me to be friends with a girl, and is it wrong for me to be friends with a 13 year old?

I will not talk about Islam in this matter, but I will talk about man and woman relationship.

There is a question, "Can a man and a woman be friend in close friendship?". Many people say, they can't, because will be hard for them to maintain the feeling as just a friend. Honestly, I agree. I've ever be friend in close friendship with three girls when I was young. And all of them then fell in love with me!. One of them later became my wife.

This is what will be happen if a man a woman too close with each other. But if only know each other and interact normally, it's okay.

yeah dude if she's reached puberty