We are often challenged, sometimes without even noticing, to bear witness to the faith. I wonder if your friend wanted to give you this information because, in part, he/she wanted to test your reaction to it. We must stand up to Satan, strong in faith, and he will flee. We are mocked as a last resort. (It is a great honor to be mocked!)
You don’t need to leave blessed objects around. Your prayers will throw open the windows and let the wind blow through. My prayer, and probably many others, will be added to yours.
I read your post about blessing your friend's house... I have to say, it's tricky. I agree partially with the apologetics answer, but if I were in your position, I would still think and pray hard to see if that really is the right thing to do. Especially pray for your friend.
Perhaps telling your friend that you feel really uneasy being in the house knowing about the witchcraft and if it would be okay if your friend "humours your superstition" and allows you to bless his/her house for your peace of heart? Most of my friends would laugh but agree if I said this really seriously and explained that I was genuinely concerned. Especially if you add: "It makes no difference to you, but it would make me VERY happy."
Hope it works out! God bless!
wine-making, music, reading
"I think nighttime is dark so you can imagine your fears with less distraction." - Calvin