It sounds like you care very much about your sister and your family. It is difficult to deal with the effects of such a traumatic background, particularly when it's still affecting everyone even after the direct family dysfunction is no longer as present.
It seems you have taken a lot of the trauma on to yourself with this situation. Your sister's response to the childhood problems has spilled over into your relationship with her and her inability to see her issues separate from you sounds poor to non existent.
Fortunately, you have a choice in how you want to respond to your sister's behavior. But, only you can decide what steps to take. You have some choices in how you want to approach your relationship with your sister and her family. You definitely do not need to accept any type of emotional abuse either directly or indirectly. Increasing your own self esteem would go a long way in helping you see what is your sister's issues and what are your own. Defining the boundaries in your relationship with your sister would also help.
How do I do this?
Here are some steps you can take to make this happen:
- Distance yourself for a predetermined period of time. During this time, do not have contact with your sister that is not planned by you. This will limit her ability to manipulate you when you are off guard. This way, it is on your terms.
- Work on your own self esteem issues. You can do this either with therapy, reading books dealing with self esteem, doing activities related to increasing your self esteem, etc. A great book is Adult Children of Abusive Parents by Stephen Farmer. It's about 12 dollars on Amazon.com.
- Talk with trusted friends and others who you can rely on to provide you with support. They may be able to give you some of the insight you need right now. If there is no one you can trust, perhaps a support group for adult abuse survivors or a different therapist could provide the support that you need.
Most of all don't blame yourself for your sister's issues. Put yourself first for a while. It may feel like you are going against your nature, but taking time to evaluate your situation and protecting yourself from further abuse is a critical step to success.
The above steps also apply to your situation with men and relationships overall. I think you will find that getting some perspective will go a long way towards solving this problem.
Hang in there and remember be good to yourself.