It could be probably a bug on iOS7. But the last button is not separated from the previous one
It seems that the initWithTitle:delegate:cancelButtonTitle:destructiveButtonTitle:otherButtonTitles: method is buggy and you shouldn't specify any cancel button here at all. Btw, it seems that a destructive button set in that method also won't work very well.
Instead of it you should:
["Action 1", "Action 2", "Close"]
or sheet.addButtonWithTitle("Close")
sheet.cancelButtonIndex = 2
Then everything will work as expected. On the iPad the button will be automatically hidden and on the iPhone it will be styled and placed in the proper way.