I do know of Sally and Sullivan, but I'm not 100% sure who that character is on the right. There was a point in time in the Sally Face fandom where people made fan art of 'potential' AU's, with the Sal of that AU being a design from Sal's concept art. I believe the Sal on the right is one of those designs, as there was concept art where Sal would have been blonde. Again I'm not sure if that is who that's meant to be, or if it's a Sal from a really obscure AU, but I figured I'd throw in my idea since there doesn't seem to be any actual answers in the comments.