I can't begin to express how sorry I am that you're having to deal with these issues. They are very damaging and loaded with multiple emotional effects.
It takes time to heal after having been exposed to this kind of treatment for so long. Give yourself that gift of time, and be gentle with yourself. It is time to become your own best friend.
Please know, too, that the experience of your family not supporting you, but rather enabling your sister, is precisely what happens in many many cases, according to what I have read. It is a tragic thing that you all had access to counselling, and that it wasn't given the chance to go very far. My family closed ranks on me in a different way; but it had a deleterious effect on practically ALL of my dealings with family, after that, and caused me untold grief, and pain on top of pain. You have my complete sympathy.
A wise, and much-beloved aunt-in-law once shared with me (a few years too late to really help, but it was validating) that confiding in, or expecting help from our immediate family is usually a dead end. It can even backfire on us, and badly. I think it's mainly because there are unacknowledged and/or unresolvable dysfunctions that are so very deeply enmeshed in the fabric of interactions, that they can never be resolved---and people experience some profound and painful dissonance around it. Just my theory. Whenever I tried to broach difficult subjects within my own immediate family, I was usually told I was either "too sensitive", or "paranoid", neither of which were true or helpful. Indeed, being told these things, simply compounded the damage. My concerns, throughout my whole life, were almost always dismissed out of hand. I don't know why I thought perhaps that would change when I was an adult of some years.
We learn as we go.
So I am really sympathetic to people who are never heard, never heeded within the family arena. That of course extends to any relationship where they might feel invisible.
I do feel like I could write a book about what it was like growing up with a narcissist for a sister. And then to slowly realize that the woman my Dad took up with after my mother's passing, shared the exact same kind of psychopathy as my sister, BUT WORSE!!...yes, I could probably also pen a screenplay for a movie. But it would be a sad one, with lots and lots of damage done, and still much repair work needed for my life. I do have a way to go, yet.
You're on your way to healing. All those other people do not matter now; not as much as you finding the comfort and the validation you have been deprived of for so long. And it cannot be overstated: It can take a while to wrap our heads around the different aspects of this pathology. Give yourself the time to do that.
I also wanted to say, it's taken me time and continual re-education, and re-enforcement, to develop my boundary-building skills. I am still working on maintaining them, as I have a tendency to want to wrap my arms around the world, forgive everybody who seems to be struggling (and I do know, my sister does struggle with this), and try and be as kind as I possibly can. But I have learned
the hard way that my sister will never respond positively to this, either. Not directness, or hardness, nor extreme and continual kindness will ever touch her conscience (not enough to make a difference). It is the way she is wired, and this, too, took me YEARS to realize.
Yeah, boundaries. Believe me, you'll need them.
You seem intelligent and kind. You'll be able to do this. I LOVE the idea of discussing it with a therapist!!! That will probably help more than anything else. You'll be out there ahead of me in no time.
Clearly, you and I are very, very different people to our sisters. And I, for one, am very glad of that fact.
Stay kind!