They aren't the same name. I like Shane a lot better. I mean I like Sean but I wouldn't use it. I would definately use Shane though. Every since I've listened to the singers ShaneBernard and ShaneEverett, I've loved the name.
What she means is . . .That they are the same name etymologically - they're both Irish versions of John. They're just pronounced differently, probably because Shane is Anglicised and Sean isn't. :-)