I need help brothers and sisters!?

My husband just found out that he may have a child from a girlfriend he had in high school. They are going to get a paternity test next week to double check... however this child looks almost exactly like my husband. The thing is, she said that if it is his child, she wants to move in with us so that they can both be parents to the kid... I don't know what to do about this. She's not Muslim and she is very irresponsible, as she spends her nights partying, drinking and smoking marijuana. I don't want to deny my husband of being with his child if it is his child, but I don't want to leave him, but I definitely without a doubt do not want her living in our house... please help. I just don't know what to do!:(