Is my step-mother narcissistic?

Hi.

I prefer not to state my age, as I am not of legal age yet. But I desperately need advice on how to deal with this.

I have noticed lately that I dread going home after school. The reason for this is because my step-mom proceeds to yell and scream at us for EVERYTHING. She also never believes or listens to anything we have to say, we being me and my siblings. For instance, she accused me of cutting my hair in the bathroom, hence why my hair was in the bathroom sink. I stated, 3-4 times, that the hair was INDEED mine, but it wasn't because I had cut my hair. It probably just fell out. She didn't believe, and constantly accused me of lying. When I still didn't 'admit' to it, she accused me of trying to get my siblings in trouble. She then told them to do punishment, since that's, according to her, what I wanted. I then told her that I didn't want that, it’s just that I truly didn't cut my hair. We yelled back and forth for a bit, and I guess she misheard me and thought that I had admitted to it. She lectured me, and told me that from now on, she would use my siblings against me whenever she thinks I'm lying, and if I don't admit to it, I'm selfish in her eyes.

This isn't the only thing, as she is also very hypocritical. She says that I am selfish, lazy, and that I care more about friends and my girlfriend more than my own family. This is again not true. My family is my number one value in my life, and I show this everyday by feeding my baby siblings, constantly putting my step moms mental health before mine, and over all doing the work she as a mother should be doing. I do all of this, while she plays video games on her phone. Her excuse for this is that her phone is the only thing brings her happiness, hence why she is always on it.

Now for my main reason for thinking she is narcissistic. She is 100% fully convinced that me, their daughter, is trying to ruin her marriage and make her seem like a bad mother in front of my dad. Basically, I'm trying to get them to separate, as seen in her eyes. This is absolutely, 100%, not true. It honestly hurt me and still hurts me every time she yells at me for it. I constantly tell her that I am not trying to do that, but all she does is just say that one day she will expose me as the sh*tty daughter I apparently am. This hurts especially because as I said, I am always trying to keep her happy. I make her breakfast in the morning without her asking, I clean her room, and I take care of her kids even if I'm tired when she is stressed. I also take care of the babies when they are crying, because whenever my baby sister throws a temper tantrum, my mom just sits there and laughs. I would do anything for my baby siblings, but I would be lying if I said that it wasn't exhausting. I don't mind doing all of this for my family, but my main problem is her always saying I'm ungrateful, lazy, and selfish. This hurts me a lot because I am constantly putting her first.

She also OPENLY favorites my sister. She said to my face one time, when she was on her lecture about how I'm trying to destroy her marriage, that she has been buying things for my sister more because apparently my dad hasn't (he has), and because I am not deserving of it. I clean and cook and watch the babies more than my sister ever does. My sister also loves to bully the two little ones, and all my mom does is tell my baby siblings that my sister is stupid. That's it. As in she doesn't lecture my sister or anything.

There is so much more, but I don't exactly have the time to remember it all or type it all out. I need advice, and if she truly is narcissistic how do I go about trying to get her help? Because if I tell my dad about this, she will accuse me of trying to villainize her in front of my dad, and chances are my dad will believe her, since she is the wife, and the wife comes first, according to my step mom. If you have any questions, please just ask. I will answer anything, just please give me advice.