Have you told this entire story to a lawyer? I would not accept anythong that may possibly be changeable. And you never saw a family law attorney to see if this csn change. So you dont know.
I tend to be proactive and not give up. I cant believe that no lawyer was involved in all this. It doesnt sound right. And the child had no lawyer either? They are called guardians.
I dont believe your grand is so happy to be with your daughter...she is horrible. She is a mess. Your grand may be scared of her or angry that you dont have her. She doesn't know what happened. Kids like stability. Then grand had your mean sister and back again. Her head must be spinning. She cant possibly understand this.
Custody battles usually require lawyers, guardians, sometimes a trial. My son had to fight for 50 percent of his sons time. He needed a lawyer. It worked.
The whole custody bit with your grand sounds fishy. Like a Friday fish fry. Like something is wrong.
Your granddaunghter doesnt understand why she isnt with you. Just because somebody gives birth to you, that does not make the person able to be a mother. Your daughter has not been a mother to any of her kids. The courts know that some mothers are unfit. That is why so many kids are in foster care, not that foster care is good....I digress.
I do think you should talk to a family law attorney. About this whole mess. It is never a good idea to go to court without representation. Grandmothers can sometimes be named legal guardians. Your daughter is already known to CPS. My guess is the Judge, with you without representation, decided you cant have cistody because she will see her mother if you do. And you without representation did not let the judge know otherwise.so sister got custody. I do t have a clue how Daughter got custody back with her history.
You need a lawyer.
Its worth a try.
Goof luck!