I invited a friend here for the summer with her kids. Her 6 months visa expires in oct and now she doesn't want to leave despite her promise to leave. What should I do and will that affect me in the future if I want to invite someone else. I don't want to be part of their being here illegally or if they get involved in something illegal.

If you sponsored her it will negatively affect you.

Try to convince her to go back in time... or call the INS and sleep with a clear conscience if she won't.