Am I jealous or is this for reals?

I been seeing this guy for 3 weeks now and this week he tells me his ex girlfriend sister is moving in for a lil bit. I have hang out with this girl. Few times and I'm a lil jealous of her. She is beautiful lots of fun. She got kicked out of her sober house now she supposably sleeps on my bf couch. Last night I was with him and she just talked my ear off. She is way too flirty with me. I called my boyfriend after work and there she was with him on speaker. Like what the F? I told her she needs I move out by Nov? But I want it to be sooner because I do not want to keep seeing her. I want my time with him not her and him? What the F ? Is happening ?