For someone as powerful as Anakin, one would think Ahsoka considered the possibility that he survived Order 66. Ahsoka had also seen Anakin flirt with the dark side as his student, and sensing the events in Palpatine's office would be familiar to those moments. While Ahsoka can't fathom the...
it's not the first time the two characters have met. During Luke's training of the child Grogu in The Book of Boba Fett episode 6, an appearance is made by Ahsoka, the former apprentice to Luke's father Anakin Skywalker. However, they're already familiar with each other...
But in the instance of the battle of Malachor, Ahsoka jumped into the fight in order to save Ezra and Kanan. Ahsoka and Darth Vader had an epic fight in the Sith Temple at Malachor. Here Ahsoka reveals her doubts about Vader's true identity and swears revenge on Vader for Anakin's loss...