I had this problem too and It's horrible.Also sad at the same time.This woman did used to turn up at my house on 9 am everyday - even weekends.
I let her in the first few times that she followed me home. I made a big mistake. She would use the children to get to me. She would not go home. I fed the children because I had to feed mine. In the end I would say I had to go out, so she would go home.
I was feeling very low with P.N.D at the time and didn't have the strength to say no. She ended up borrowing money ( for milk for the children) eevn though she smoked ect.She never gave it back. We had nothing in common and I feel she used me tbh.
I went to assertive classes in the end to deal with this sort of thing. I think I felt responsible for the children really. They were very dirty ect. While it was going on I felt invaded and angry.
So, I feel for you. Follow your instincts from the start. She is not your problem.She will find her own friends eventually. Have a quick chat and thats it. . By the way this woman ended up stealing things from my house.