Ok, I am assuming from your line “of different religion” that you both are not Catholic?!
In any case, yes the show is about witchcraft. Just as Buffy and Angel are about Vampires, Nether world demons, etc. You can look at it in two ways, it’s fiction or are you enabling this evil to continue.
First, Fiction! Yes, this can be watched for the enjoyment factor, watching the way the sisters bond, yadda yadda yadda. As long as you find it to be fiction like reading a Stephen King novel. The problem would arise on if you started to believe in this over God. By using witchcraft, you could be telling God you think you are a god, can control things around you, and then you find yourself in a mess of trouble with nearly all the seven deadly sins.
Second, enabling the evil to go on. There is a strong showing in our society that if you become exposed to something long enough, it becomes normal. For example look at television. Fifty years ago June Cleaver slept in a twin bed without her husband, now you have to look hard for a tv show that does not show pre-marital sex or illicit behavior. Now Hollywood wants your dollars, so they are putting stuff out that they think you want to see, it is up to us to let them know we do not want to see a good portion of what they are producing.
One of the threads in the “Ask An Appologist” forum had a question on “Should I not watch horror show/films”. Look for that one for more details, it might be a few pages back!
Good Luck and pray about it. God wants to speak to you if you want to listen.