My p 0 r n addiction and my nice plus sister inlaw

Hi I have a p 0 r n addiction and sex addiction. I live with my sister inlaw and her daughter which is my niece and she is 10yold.
Me and sister inlaw have sex at times but when she's not there, I go to my room and spank the monkey while watching p 0 r n.

The other problem is that when me and my sister inlaw was having sex, my niece was watching us.
I didn't know until I blew in my sister inlaw and she got off me.
As awkward it was, her mother tells me it's fine if she saw us have sex Because she allows her daughter to watch p 0 r n.

Other night I saw my niece in the living room watching p 0 r n and playing with yourself, spanking the monkey and sister inlaw says girls at that age have lots of hormones and need to experience things.
It's a part of growing up and life.

What do I do? Should I not intervene and let her?
Because who am I to tell her as I have a p 0 r n addiction and my words wont do anything and mom is ok with her.