Can I tell her not to bring her kid to my house anymore?
What's wrong with having the kid over?
It has gotten out of control since it seems to be disturbing my household environment.
It's your house, so you have every right to set boundaries when it comes to other people. If the kids are being troublesome, you have the right to exclude them when the person visits.
Oh, I would never do anything like that to them. I'm a pussy, no way in hell. I need to get over it since I am too scared to move away.
You should just tell her not to bring her kids over anymore if this is how you're feeling about it. It is your house, so you can always bar anyone from where you live if you own the home.