My intuitive, immediate response is: Of course! Absolutely. But then I read this:
I don't know, I'm always trying to second guess them instead of trying to be human and 'normal'. Probably because all my attempts to be human and normal have failed over and over again.
JW's are so good at framing the situation that no matter what we do, it's wrong--at least from their perspective.
That being said, my thoughts are this: do the right thing, the thing that makes YOU feel good: your normal.
Perhaps a card or a letter would be more personal than a text. I'm kind of old fashioned that way.
Sorry about your sister. This cult ruins so many things. You care, that's evident. Don't let their bad, dysfunctional behavior define you. You are an amazing, sensitive and caring person.
Although I understand what other posters have written about the futility and dangers of "chasing a relationship" with people that have treated us badly, I have another perspective on that. Letting your sister know that--in spite of how she has mistreated you--you still care. That's all. It's just letting her know you care. Nothing more, nothing less.
jp