A frienemy is an enemy of yours that can also be friendly, but nonetheless, you hate them. They are also friends that are so nice and friendly, they annoy you to the point that you hate them, and they are your enemy.
your girlfriends best friend who hates you and you hate as well, or vise versa. anyone who agrees to act somewhat respectfull to a person as they do the same with the understanding that they both hate eachother
girlfriends best friend: i hate you
boyfriend: i hate you too bitch
girlfriends best friend: let's be frienemys
boyfriend: ok