Do I have any rights to stop this?

Me and my girlfriend have been together for 3 1/2 years now. My oldest son came to live with us right after we got together, then shortly after my youngest 2 children came to stay with me cause the mother was unable to care for them. After a few months she came and got them just so she could get child support. Now in March will be 2 years we have had my 2 youngest again only this time I got a Lawyer and got my kids. My girlfriend is very good to my kids and takes very good care of them. She does all for them that a mother should do for their child. My girlfriend is a reefer smoker she smokes marijuana but it does not affect her ability to do anything that she has to do. She still cooks, cleans, washes clothes and cares for everyone in our house and all together there is 7 of us, me, her, my three kids and her 2. Now the mother of my 2 youngest started rumors about me and her trying to get rid of the girlfriend when that did not work then she called cps on my girlfriend for smokin and drinkin and abusing my kids. My kids have never seen her do it they know nothing of it. I am a plant worker so I am clean and take random tests. I feel as long as I don't have a problem with it and my children are being takin very good care of and do not want for anything that she should be left alone. As a parent I would not allow something to go on if it was hurting my children but my kids love her like she was their mother. Someone please help me before my family falls apart.