Is 17 too old for a 13 year old?....

HI look im 15 and i say yes he is way to old for you. yea you like him and he may like you but he can go to jail if anyone found out. and i dont think you want that to happen do you.

but whats the difference betwwen me and him and lets say a 20 and 24 year old? :-(

the main reason is the developmental level between 17 and 13. People of these ages differ greatly in both maturity and physical matters. Generally, the younger the ages, the more of a difference it is. When you're over 40, there can be as much as a twenty year difference, however people 12-16 should only be dating up to one year apart. If you're still not satisfied, and you feel that a four year difference doesn't matter in any case, look at 13 and 9.

Source: My older brother was on the other end of the spectrum. He understood that a young girl had a crush on him, and was somewhat okay if they remained only friends, but he harbored no feelings for her. So... yeah.
I hope I've helped

In my opinion, apart from the law, I dont think he is too old for you. You both are teens. Just make sure he is a decent bloke.

a bit too text bookish. We are talking emotions and affections here. Such things don't follow man made rules because each of us is wired differently.
She likes the guy and he likes her a lot. Nature and biology has designed us to have such feelings once we hit puberty and teen years. I think it is a beautiful construct and I would respect how biology works NOT artificial man made, society driven rules. Rules are all about control NOT commonsense.
I think she should follow her heart BUT take precautions and be prepared ie learn about pregnancy and STDs and her own needs. The most important thing is for them not to end up with the girl pregnant or transmitting STDs. No one needs to know if they like each other and decide to have sex. Whats the big deal.