Hi and welcome. I'm a recovering opiate/crack/cocaine addict, 10 months clean. My addiction to cocaine (powder) eventually lead to crack cocaine abuse. In 18 months of smoking it, I almost lost everything, including my life.
I, for one, would go into the bathroom and perform all the rituals that your friend is doing; running water, a fan, etc. I would always either have a scented candle burning, or air freshner. The point, for me in running water was so it sounded like I was actually in the bathroom for legit reasons. It would also help with the sound of flicking the lighter so much, so no one could hear me. I would also flush the toilet a lot....I'd take a hit, hold it, and blow the smoke in the toilet as I flushed to cut down the smell.
I also have a window in the bathroom that I would quietly open and shut.
This worked for me for quite a while, as my husband was clueless to the fact I was 'smoking it'. He thought that I was snorting it.
Crack addiction is a tough one to beat...it's definately something that you have to really truly WANT to QUIT.
Good luck to you.
Penny