Wiccan culture... it's basically the mortal's pipedream of harvesting any form of magic or being connected to it. Some aspects of it, they're not too far off. But unless you're a magic user, being a Wiccan would just be shooting blanks. 
And out of all the possibilities of what Mirela would have to deal with in a roommate, wiccan was not on the list. 
Now she would have to be extra careful around Gosia, as the tiniest magic related thing would probably set off her curiosity. Nevertheless, it wouldn't make Mirela any the more distant or hostile towards Gosia. After all, Mirela wanted to live alongside non-magic humans. 

"Oh wow, I've never met someone who was a Wiccan. I honestly barely understand it. So my future apologies if I ever come off ignorant." Mirela takes a closer look at Gosia's pendant. Nothing about it seemed at all magical. Though it would make sense for Gosia to have more faith in it protecting her. When one puts a strong attachment towards an object, their view on life while with their "lucky" possession would fare much better than without it.