AIO for kicking my sister out for smoking in my house after she lost her job?

I (34M) let my sister (30F) stay with me and my family after she lost her job about a month ago. I didn’t charge her rent and was trying to help her get back on her feet.

After she moved in, I noticed cigarette smoke inside the house. I have kids, so this was a problem for me. I spoke to her about it and told her I didn’t want her smoking in the house because of the kids.

Despite that, it continued. She sometimes denied it, sometimes downplayed it. The situation finally blew up when she lit a cigarette in front of me and my kids. That made me angry, because at that point it wasn’t accidental or hidden—it was blatant.

I told her again that this wasn’t okay. After that incident, I told her she needed to leave. I didn’t scream or get physical, but I was firm. I said I wasn’t going to risk my kids’ health or keep repeating myself in my own home.

Afterward, my mom got furious at me and said I was cruel for kicking my sister out when she’s already struggling. But my mom also doesn’t want my sister staying with her either, saying she “can’t deal with her right now.”

Now I’m being treated like I overreacted and abandoned my sister, even though I feel like I set a clear boundary, it was ignored multiple times, and I only acted once it crossed a line in front of my kids.

Am I overreacting?