Thank you for the added information. It helps a lot. I believe I can now be of help with this issue.
First, let me say I can imagine how frustrating this situation must be for you. Because clearly you and they have gotten into a "vicious cycle". What do I mean?
You want them to love you. So when they ask you for money and things, you say yes. You get resentful. But now that you've said yes again, they understand they still have power over you and so they take this as you encouraging them to keep asking in the future. So they ask again. And the cycle repeats.
And this is actually the key to my answer to you that you need to consider and think about. You are buying their love. I know I am being very open and honest with you here. But we can't get you out of this vicious cycle if we are not honest in facing what's going on. And what's going on is that you are buying having a relationship with them. Let's face it:
You don't have to leave town and change your phone numbers. If you would start saying no, they will soon stop calling you. They'll stop having any relationship with you. They'll try to tell you what a bad sibling you are, what a bad human being. But after a while, they'll disappear themselves. Why?
Because they aren't getting what they are seeking. It's possible that if many years ago you would have said no that they would have just expected that you are not there to be used but are a relative. But that's doubtful. They seem very, very self centered and selfish.
So let's address the two main things you write that you will have to correct if you want to get over this. Because I doubt very much you're going to leave town and change your numbers. But if you actually will do that, I will support you in that.
The first thing is that you say you can't just leave your niece in jail. Why not? Because you'll feel guilty. But you miss the main problem here: enabling. Your bailing her out of jail is enabling her to continue with her bad behavior and to use up police time, etc. without changing her life. Because she knows you'll bail her out. That's not healthy for HER. You might feel better, but it is not helping your niece. This is the problem with enabling.
Next, let's discuss the main problem you bring up: they have power over you because you've been doing it so long and they expect it. That's saying they have power over you because you can't bear to say no. But again, that's enabling them. Because you can't say no, because you keep wanting to buy affection and family love you are enabling people to be users and to behave badly. That's not healthy. For them or for you.
Here are two important and good books you can recommend she get from the library or buy online or from a bookstore about enabling:
Setting Boundaries with Your Adult Children: Six Steps to Hope and Healing for Struggling Parents by Allison Bottke. She comes from a Christian perspective but it is not a religious book and non-religious people have found it extremely helpful. Now your sister and your niece are not your children, but the principles are EXACTLY the same. And you're acting like they're your children: like you're a well they come to whenever they want anything, and they dip into you and pull out whatever they want. This is not healthy.
The Enabler by Angelyn Miller. This is also excellent and not just for the usual enabling of alcoholism, etc.
Okay, again, if you would really be willing to move and change identities, then I'd agree. But I don't think it's practical and I can't imagine you'll really do that. So instead, please consider learning about enabling behavior and stop doing this. Just because your sister is controlling that doesn't say anything about YOU. You are the one who controls your actions. And you so far are too afraid to lose their love even if it's bought love. That needs to change for your own wellbeing and for theirs as well.
I wish you the very best!
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