Ahsoka came out that ship on Christophsis already strong-willed, stubborn, sassy and cunning. She SOOOOO would have ignored Yoda's instructructions and not correct Obi-Wan when he introduced himself to her as her Jedi Master.
Because i mean... i know the war was still new, but it HAD been going on a for at least a half a year before Ahsoka showed up. you telling me if this child had a choice, she would choose to be the padawan of a freshly made Knight over a season Jedi Master? especially one as high ranking and infamous as Obi-Wan Kenobi?
Obi-Wan: Hello little one, I am Obi-Wan Kenobi and I am your new Master :D
Anakin: *ew kids lookin ass* ...hi.
Ahsoka, knowing full well she is supposed to train with an Anakin Skywalker: ... yes. Obi-Wan Kenobi, I was assigned to be your Padawan. yours specifically. no one else :)
Yoda: Assigned to Anakin Skywalker, Ahsoka was.
Obi-Wan: too late we bonded.
Ahsoka, koalaing to his side: mine.
Cody: our CMO has informed us the Commander has imprinted on the General sir. it would be unhealthy to separate them now.
Yoda, knowing togutas do no imprint, also knowing when he's lost: The force's will, this is.