AIO: I cut my sister off because she refuses to take any blame for bad situation

Hold on, this could be a long one. I (46f) have worked as a shift supervisor, and my sister is one of my part time workers. She’s not really my sister, but we’ve called each other sisters for the last 12 years because we’ve been super close. She hasn’t had a great relationship with her real sisters, due to a lot of abuse and trauma. I’ve always tried to be supportive of the situation and I know she has anger, abandonment, and authority issues. She’s a few years older than me, and for the last few years, she’s become difficult to handle. She’s always in a somewhat feral state, constantly inattentive, lashes out at people, and has become increasingly irresponsible with her jobs, including the one we work(ed) together. A few weeks ago, she’s no call/no showed for a shift, and as a result, we were left short staffed on a busy day. Surprisingly, the day was calmer than usual, and I commented to my coworkers how much less chaotic it was without my sister. We saw each other the next morning, and after seeing her, I turned off my phone due to a headache. When I turned it back on, she had text bombed me, telling me that someone at work had said I was laughing about her, making fun of her mental illness, and a bunch of stuff I never said. I apologized to her that I had talked about her, explained what had happened, and tried to smooth things out. She continued to be aggressive, told me I lacked integrity, and refused to let up. At this point, I told her that I hadn’t felt good about how she treats me either, and she refused to accept anything I had said, trying to invalidate my feelings. She then took my words and twisted them and called me a bunch of terrible things. My feelings are my feelings, and I refused to let her control this narrative anymore, so I cut her off, blocked her texts and social media, and haven’t spoken to her since. So, am I overreacting?