Is it normal for stepmothers to think of stepdaughts a rivals?

Is it normal for stepmothers to think of their stepdaughters as concubines of her husband??? I mean he is my real father how can she think that???

Long story:
My stepmothers is super jealous. I can say that because she is very open about it. Just yesterday when i came to visit my father after a year she was very angry. She did not talk to me and not even my father. So last night when my father had gone to bed and i was awake watching TV in the living room, she just came and sat beside me. So i tried starting a conversation and stared talking about my work and then she said something about her work. So in the middle of the conversation she became very hateful for no reason. And said i should not come and visit my fathers house anymore cus she sees me as a his concubine. and i,m like wtf??!!! and from there it a huge fight started.
is it normal for stepmothers to think of their stepmother as concubines of their husband who is actually their father???