People do not change

I just spent a few days with family on the other coast. It was a wonderful trip as it's always good to be in New England and I really do miss my sisters and bros.
We're the older generation now and that sucks..oh well.
Out of the blue (I'm sure it took all she could muster), my youngest sister brought up moving in with the significant other. She quickly followed up the announcement with, "She has changed". (Is it the result of a very sad event in her family?) Another sister and and I sat with our jaws hitting the lovely hardwood floors, in shock.
This changed person is the one I saw verbally tear apart a teenage host at a restaurant the night before, because we sat down for pizza a few minutes later than he originally told us!
I know this one little event is not a big deal in itself but it is a reflection of something more. It is a behavior that we grew up with and feared constantly. It's an extension of emotional abuse. The poor public behavior witnessed is the same one drilled into you at home. You become the one not doing it right, the lazy ass, the one that doesn't get it. "You're lucky I'm here. No one else will put up with this!"
My sweetie sister has been putting up with this shit for a few years, without having made a commitment. She was slowly developing her vertebrae and taking the crap less and less. Now, because the abuser is melancholy, she's changed?
Dammit, people do not change!