Curse from a Rose (Spoilers)

In the extended Halloween "movie" that ended Season Six, we meet Autumn, Cassie's college room mate.

Is Autumn a witch?

We first see her in a candlelit room reading a poem from an old family book. It seems like she's performing some kind of incantation. Later she enters Abigail's flower shop after hours, when the door is locked, but she doesn't appear to have a key or to have picked the lock--it looks like she just effortlessly opened the door. The next day Abigail finds all of the roses dead and dried out. How did Autumn cause that to happen? It can even be inferred that she had something to do with the rain storm that soaked the firewood.

Yet although Cassie seems to know what's going on, she never hints that Autumn is a witch.