Am I wrong to tell her to get out if she gets pregnant

My sister and her boyfriend lives with me, my husband and our two kids. Her boyfriend works but he doesn't pay anything. She doesn't help clean. She just sits on her ass all day. They've been staying for a couple months and show no sign of leaving. She recently told me her and her boyfriend want to have a baby. I asked if she's moving out and she said she wasn't planning on it. I told her no, we don't have room here for a baby. She said I can't tell her what to do. She wants a baby, she's gonna have a baby. I told her if she gets pregnant she's out. We don't have room in this house for another baby and also this wasn't supposed to be a permanent stay and shes making is sound like she never plans on leaving. She says I'm trying to control her body. I'm not, but she's not gonna move in my house, not pay for shit and bring an extra mouth to feed.