No, you've got the timeline right re: Vriska. Briefly, the timeline is: she jumped Tavros off a cliff, Aradia sent ghosts after her, she mind controlled Sollux into eating mind honey and showing up at Aradia's hive, where the mind honey caused him to kill her, Terezi (with Sollux's help) contacted Doc Scratch who blew up the ball in Vriska's face, then lots of time passed ("sweeps" the text says, so years). Then in the game, Aradia beat up Vriska, the game was won then lost, and now here we are.

Ah-ha! So I assume Aradia killed Vriska (maybe not intentionally but damn that was a bad beating) and dream Vriska took regular Vriska’s place. 

And maybe Aradia wanted that to happen? She doesn’t seem the beat someone to death just for revenge type.