I liked Ashley: she was playing her own game the best she could given her options. She knew Rob had to go, but her options were limited because the Buddy System prevented her from talking to Zapatera. From the edit, she’s the only one who tried, but Rob found out which put her on his radar. She won two crucial Immunities when she was eventually in Rob’s crosshairs.
That Tribal (Top 5) was the last time Rob could play his Idol, so he was safe and Ashley knew it.
At the Top 6 where Andrea was first voted out, Rob had Immunity.
At the original Top 5, Ashley could have taken a shot at Rob, but her only option was to work with Grant and Natalie, and Grant was Rob’s “buddy” which limited/negated her time to talk to him. He also seemed pretty hoodwinked by Rob, given his reunion appearance. And even if she did pull this off, Rob would have had a duel the very next day against Andrea and Matt to get back into the game.
Ashley was seconds behind Rob in the puzzle for Final Four Immunity. Even though she lost, her relationship with Natalie rivalled Rob’s, and there is a chance of forcing a tie with Phillip. Does Ashley beat Rob? Given how much the jury despised him, it is a solid possibility she’d be seen as a palatable alternative.
There are tiny things Ashley could have done differently (build a stronger relationship with Phillip or Andrea), but even with those changes, her best shot at a win was to beat Rob at Final 4 where he’s unprotected, or use her relationship with Natalie to slide into the finals.
tl;dr: I don’t think it’s accurate to lump Ashley into “Rob’s Zombies”.