Huummmm?? ??????????????????????????

If she's a good best friend she'll be supportive of you and have no problem with you two dating. There is nothing wrong with it...and I honestly don't think it would jeprodize anything, even if you do date him and things don't work out. And if it DOES jeprodize something, then you obviously weren't really that close to all of them, because they would still like you and be friends with you no matter what. That's what good friends do.