In Rebels, she felt Anakin's presence when she tried to feel Vader through the Force. The overwhelming realization caused her to faint. Later, she fully realized and accepted Anakin was now Vader.
Darth Vader's true identity as Anakin Skywalker was a highly guarded secret, known only to a select few individuals including Palpatine, Obi-Wan Kenobi, Luke, Han, Leia, R2-D2, C-3PO, Master Yoda, Bail Organa, Ahsoka Tano, Darth Maul, Grand Moff Tarkin, Grand Admiral Thrawn, Jocasta Nu, Ferren Barr, Verla, Reva, ...
Very few people knew that Darth Vader and Anakin Skywalker were the same person up to his death in 5 ABY. Imperials who knew in the current canon: Sidious (emperor), Grand Moff Tarkin, all or most of the Inquisitors, Grand Admiral Thrawn, various clones in the early empire.
What happened to Ahsoka after Anakin became Darth Vader?
As the events of The Revenge of the Sith played out and Anakin turned to the Dark Side and became Darth Vader, The Clone Wars series showed that Ahsoka was off fighting to retake the planet Mandalore from Darth Maul, who was revealed in the show to have survived his seemingly fatal duel with Obi-Wan Kenobi on Naboo.
Summary. Ahsoka Tano believed Anakin Skywalker was dead after Order 66 because she couldn't sense his presence in the Force anymore. Ahsoka had seen Anakin flirt with the dark side before, but couldn't fathom that he would betray everyone.
She certainly knew something. The “I know. More than you realize, I know” line makes that clear, as does the Forces of Destiny short with Anakin, Padme, and Ashoka.
Ahsoka's portrayal of Anakin with a red lightsaber fulfills the promise that Revenge of the Sith couldn't deliver, showcasing the version of Anakin who would become the most powerful being in the galaxy.
The two had recently parted ways for what would turn out to be the last time, at least until their fateful reunion in Star Wars Rebels. But as he journeys through Ahsoka's memories, Anakin is able to see the warrior and leader Ahsoka became by the end of the Clone Wars. He taught her to be a fighter and a survivor.
Yup. Anakin's vision of Padme's death is the main catalyst behind Anakin turning to the dark side. Ahsoka staying or leaving is irrelevant next to Anakin's unhealthy attachment to Padme.
And while his warnings don't work, at the very least, it shows that Maul became aware of Anakin and what he would soon become. With the rise of the Empire, it's likely Maul caught on to Vader's existence pretty quickly.
R2-D2 was present when Padmé gave birth to Leia and Luke, so he knew Luke was Anakin's son – but what he didn't know was that Anakin became Darth Vader. In addition to that, Anakin's fall was surely a painful event in R2-D2's life, one that he definitely wouldn't like to remember or even talk about.
Summary. A disturbing theory suggests that Darth Vader kept one of Ahsoka Tano's lightsabers for a darker reason, potentially using its kyber crystal to improve his own blade.
Yoda. Yoda's knowledge of Luke Skywalker's true parentage was also confirmed in Return of the Jedi. As with Obi-Wan, Yoda believed that Anakin's fall to the dark side made him unsalvageable, with the Darth Vader persona being his only identity following his ascension to Sith Lordship.
Anakin Skywalker showdown would end in Ahsoka's favor. It is likely that, at the peak of his power, Anakin Skywalker would always have bested his old Padawan.
Years later, when Ahsoka learns of her master's transformation into Darth Vader on Rebels, she partially blames herself for Anakin's turn to the dark side and holds some regret for leaving him and the Order behind.
Just as Anakin's Force Ghost looked on Luke Skywalker with pride at the end of Return of the Jedi, his spirit did the same for Ahsoka, confirming that Peridea was where she needed to be. Force Ghosts only speak when a Jedi needs guidance, and since Anakin didn't say anything to Ahsoka, she no longer needed his help.
Anakin's final lesson helps Ahsoka redefine herself beyond just being a weapon and a soldier, embracing her desire to protect and fight for what she believes in, completing her Jedi journey.
Anakin does not have even the slightest bit of remorse. By the end, he feels nothing but anger. Although he feels regret for killing Padme, he still helps the evil Emperor. The film ends with Anakins standing side by side with the man on whose behalf he has committed all his crimes.
starwars.wikia.com/wiki/Wilhuff_Tarkin is a smart guy, and eventually deduced Palp's true identity on his own. Likewise, starwars.wikia.com/wiki/Ahsoka_Tano figured it out after Order 66 as well.
Summary. Luke Skywalker and Ahsoka Tano have already met in The Book of Boba Fett, suggesting a previous encounter in the Star Wars timeline. The possibility of Luke and Ahsoka meeting exists either before Return of the Jedi or during the years following the fall of the Empire.
