I haven't talked to either because I'm pretty sure that they really don't care. If I do they won't even like do anything to help most likely.
I'm inclined to agree with you about the separation anxiety with your sister and your parents, which is completely normal. As far as how specifically to handle this, I wonder if you have talked to your sister and/or parents about this yet, perhaps you can all come up with ways to deal with this adjustment together.
I'm just thinking like something bad will happen and I'll never be able to see her again. Sometimes I feel like I would have to like do something just for her to have a reason to like come home. I also have the feeling even like maybe it's separation anxiety or whatever with her and my parents.
I'm not sure what specifically to tell you, you seem aware that you're worried that she'll go away and not come back. What do you think is going to happen to her?