Does this sound like shes using him?

I dont know if this is just me so i'm going to ask you ladies. My dad dated this girl when I was about 4 until I was 10. I hated her. She was mean. She hated me, always called me a sppiled brat, and gave me dirty looks, and made me feel like he didn't love me. Of course he didn't see it. He said she loved me and I was over reacting. They broke up for 3 years because I think she cheated on him or something. He didnt talk to her and I was happy because I had my dad back. I was the only girl.. And I liked that. I know, I was spoiled. But now, i'm 17, and pregnant. They are together and have been for a while. She lives here. When she moved in it was good. She was nice, and we got along. She worked and bought the food and cleaned while he payed the bills and did all the work that needed done. They were really happy. Then she quit her job. So my dad now pays everything. She does cook (not very good) but still. She cooks and cleans. But other than that, nothing. She doesnt respect him I guess. When he goes to sleep, she sleeps on the couch alot. She doesnt really offer to help him. She has a part time job now and she doesnt pay him for rent, doesnt buy food or help him out while he works everyday to support us and pay child support. When we go to the store, she'll pick out all the things she wants, even a few expensive things. She doesnt offer to pay for them. She wont even help put groceries in the car. When we go out to eat, she doesnt offer either. He'll make a joke about it and she'll say "Nope I dont have any money." When she actually does. Shes very rude to me saying things like i'm not feeding my baby because I dont eat alot and my fiance should pay child support even though we plan on living together and have a wedding date set. She says I dont understand anything about pregnancy when, every pregnancy is different and my doctor even says im fine and healthy but she says im not. Next week we are going on a week vacation to my fiances military graduation and she was saying how she wont help my dad pay for anything, she wont even drive so he can get a little sleep since it's 10 hours. She said we have to stop ever hour so she can smoke and now shes saying she might not go so she doesnt have to listen to me.
I just feel like she can be rude to me all she wants but she doesnt offer to help him at all and she never has. That really bothers me but my dads too nice to say anything. I even told my mom i wont be living here when the babys born because I cant stand her but I know that will hurt my dad. Does it sound like shes wrong or is it just me?