I need to get this out, because this moment baffled me at first.
Vi is convinced that she's lost everyone, and it's not quite her lowest, but she is turning all the pain of having lost her sister and her happy little family from Act 2 onto herself. I always make the wrong choice and because of that I've lost everyone.
And she starts this little vent off with Go on, say I told you so.
She thinks Caitlyn is here to berate her for siding with her sister again, but Caitlyn surprises her. Caitlyn instead comes clean about having known all along that Vi was going to choose her sister.
And not only did she know, but that she supported it.
Caitlyn went "vi is going to try and break her sister out. i will remove the barriers to their reunion."
SO from Vi's perspective, she's just had her resurrected father die, her sister walk away--choose to leave--and now she might lose Caitlyn too because Vi "chose wrong" again, BUT instead she is met with acceptance. And this is more than Caitlyn accepting that Vi is always going to choose her sister, this is also Caitlyn accepting that Vi is going to fuck up (something Vander didn't give her much room for with all that leader talk) and accepting just how much Vi's family means to her. This one act washes away all that "its her blood in your veins" crap.
This was Caitlyn fully accepting who Vi is and who she's been and where she's from. And she did it with a smirk and some swagger.
Yeah, I'd of grabbed her and kissed her too even if that was .5 seconds after my sister basically said she was going to end it all.