I found my sister on YouTube after being estranged from the family for almost her entire life. I want to reach out, but I don't know if it's appropriate.

EDIT: I want to thank everyone for the kind advice and support, and those who have shared their own similar experiences with me. I am reading every comment. Y'all have given me a lot of perspective, and I feel like I'll be able to make a thoughtful choice.
tl;dr: I (28 NB, AFAB) found my sister (18 F), who I haven't spoken to in at least four years, on YouTube today. I want to reach out but I don't know if there's any chance of a relationship because our abusive mom (50 F) has likely been badmouthing me her entire life.
Sorry, this is long but I feel like the details are important.
I grew up in an extremely abusive family, with my mom being the most abusive. I was diagnosed with PTSD from my childhood at 18, which is also when I cut off contact with my mom entirely. I won't go into the details here but it was very, very bad. I am in therapy and actively working towards trying to heal.
A little bit of background on my family: I had a brother who was 4 years older than me. He was treated very well by our mother and got away with a lot more than I did. My little sister was born when I was 11, and our parents divorced three years later.
I never had a relationship with my sister. I was, I'm ashamed to say, completely resentful of her when she was born. One of my mom's "things" was always telling me how ugly and "less than" I was for being born female. Then this new girl baby comes along and my mom says she's beautiful, perfect, gives her a beautiful, unusual name with deep meaning. My sister was also extremely colicky and did not sleep for more than half an hour at a time for the first year of her life. There was always a screaming baby in the house and I pretty much lived in my room to avoid everything.
By the time my sister was 6, I was out of the house. I no longer resented her at that point, but didn't know how to talk to her or relate to her. At 5 she had her first laptop and cellphone. I watched my mom make her exactly what she wanted for dinner every night when I was no longer being fed, being screamed at any time I tried to get myself food from the pantry, and having my mom drag me to the scale to weigh me every few days.
I didn't see her again for a few years, she was maybe 9. I still had a strained relationship with my maternal grandparents, and they had brought her to visit. She was so sweet and peppy, happy to see me. I was so happy to see her, too, but it still felt like trying to get to know a stranger. How do you bond with a 9 year old when you're 20?
I only saw her a few more times in the next five years. She got a Facebook when she was super young, like 10 or 11. We had a very superficial relationship where we mostly just sent each other pictures of cute animals. The whole time I felt like I was just waiting for her to be old enough to really talk to, explain that me being absent from her life wasn't anything to do with her and I really did want to be her big sister.
I was blocked from her Facebook pretty fast after connecting, and her phone number stopped working. I figured my mom had blocked me from them.
I saw my sister again when she was 14. Again, super bright, happy kid. It was so obvious we had completely different lives. She was in all the clubs at school, she was an up and coming musician, my mom was letting her hang out with older local bands and throwing big parties with them to get my sister's name out there. My grandparent's house was covered in professional photographs of my sister, who was also wanting to be a model. She owned several expensive guitars, had just gotten a puppy. Mom was on stepdad 2 or 3 at that point and my grandparents bought them a big nice house. A completely different world than I grew up in.
My sister added me on Instagram and gave me her new number. We talked for a few months off and on, and some of our conversations touched on me being absent. She was always super, overly polite in her responses to it, she had a lot of walls up. I understood and didn't want to push anything, I was just happy we could talk. I figured whenever the time was right she'd let me know and we could start talking about the more complicated family stuff.
But then one night my mom came over to my grandparents house while myself, my husband, and my kids were there visiting. This had been a huge point of contention with my grandparents; they wouldn't enforce my boundaries about my mother. I told them over and over I didn't want to see her.
It's a long story, but there was a huge blow up. My uncle, who was trying to defend me, blocked my mom at the doorway and yelled at her to leave; she knew I was going to be there and she knew she wasn't supposed to come. My grandfather was screaming at my uncle to "get out of his house". My grandma just sat there and started wailing. I was frantically trying to put dishes away and get my kids' shoes to bail the hell out, when suddenly my sister was in front of me. She looked concerned and confused. I gave her a quick hug, put my hands on her shoulders and said something dumb, I think it was "sorry, chaos", and then immediately returned my focus to getting my kids out of there.
Afterwards when I got home, I remembered my sister and felt bad in my gut about that weird short interaction I had with her. I sent her a text that said, "I'm so sorry you had to see that, are you okay?"
She never responded, and I've never heard from her since.
I've since cut off contact with my entire family. They have this weird cult mindset about my mom and all insist I've been lying about my abuse since I was 4 years old for attention. I've been in a much better place without them.
I still think about my sister, though. I feel like we never had a chance at a relationship. I highly suspect my mom caused that uproar that night intentionally with my sister there to put her off of me. I know in my bones that my mom has fed my sister the narrative that I'm crazy, unstable, a liar.
I saw an old comment from my sister on my Facebook memories this morning and did some light digging on social media. I found her musician's page on YouTube. I want to reach out, but I have no idea if it's appropriate. For all I know she could think I'm dangerous and she's scared of me.
I'm moving across the country in six weeks. I guess this feels like it could be a last chance to connect with her or see her.
Would I be crossing an inappropriate boundary by reaching out to her? I'm heartbroken, but I don't want to put that on her.


Source.