I'm at the Bound Until Death quest for the Dark Brotherhood and want to do it with the bonus task (balcony kill).

It's not a problem to kill the bride, but I haven't find a place to do it from without getting a 1000 gold (sometimes +40) bounty instantly. Everytime the guards will chase me, even when I'm using an invisibility potion.
Of course I'm sneaking and kill her with one shot.

Places I tried:

• other balcony where that bow is

• on the castle wall, going through the church

• from behind her ;-)

Is it possible to "stay in the dark"?

Oh, and do I have to worry about my argonian friend?