How to I tell my sister no, and still have her talk with me?

I have edited ** pictures of her as a favor. Then she ask for a photo show for her BF's birthday gift.
She brought me the SD cards today and wants me ot edit the footage add some music and do some slow motion shots.
I am to make sure I do not get the wrong person in the shots, Just her and her BF.
On the cards is almost six hours of her having ** with an old bf, a three way with her ex and my cousin, including her having lesbians ** with our cousin alone.
Then I found some of her and her new BF mixed in between those of the old bf.
I told her this is disgusting to watch, especially when it does a close up of her ** with some guys ** in it. The hearing her moan and ** our cousins ** just turns my stomach.
She told me there was an over lap when she was dating both guys. I ask who held the camera for the close ups? she told my cousin and some times her BF's buddy. I was to make sure the NOT to show the old BF's and his friend with her, and to not show any of his ** in her. That guy is the brother of her new BF and it had a tatt on the side of it. Her New BF would know who that was.
And at the end show our cousin giving her some head, she plans to see if the new BF will like her to join them.
My sister is a sick ** who had had several STD's a few abortions and been found on the side of the road a few times. She has been ** and said she liked it.
How do I not do this and still have her talk with me?