Is there any way that she can grant me full custody without having to involve the court?

My ex-wife and I have joint custody of my 5 year old daughter. Her mother had primary residency for school purposes. Child Protective Services were recently call on my ex and she tested positive for numerous drugs. There was no removal order from CPS but I was informally granted full custody until her mother has several clean drug tests. My daughter is now living in our home full time. CPS informed me that I would need to go through the courts to actually be granted full custody. Her mother stated that she doesn't want to have any custody of my daughter anymore as she is no shape to be able to care for her. She would only want her on the weekends. I am not looking for any kind of child support at this time. I may go that route in the future when things settle down. I know that she has no money and my funds are tight now that I have 4 kids living in my home. Thanks for the advice.