Of course different people have different advice, so you will get a variety here.
I get the feeling you are really worried and think the problems concerning your baby granddaughter are of the 'important' type.
Naturally you dont want to disclose too much, so do you think you could talk to your GP about how you are coping and ask for advice on support organisations you could ring?
It seems to me you need a safe place to air your worries and get some overview of them.
Not necessarily that you feel you have to do anything for the time being.
Just to get a grasp of whats happening and how to understand how you need to proceed?
I'm not in your position, exactly but families are complicated things to negotiate sometimes, and I know about that!
I also know how it feels to be unsure and afraid of the future, and I'm sorry you are feeling like that.
Some other GNet's may have much better advice, I hope they come along soon.