Anakin saved Ahsoka

It makes sense that Anakin was able to pull Ahsoka into the World between Worlds. It was established that she was in a real place, not just in her head. I've read about a theory that Mortis and WbW are part of the same plane of existence. Anakin and Ahsoka have both been to Mortis.

Since they have such a strong bond, Anakin becoming the Father when he died, was able to pull her in. He did so to give her peace of mind, to alleviate all her hesitations. She started smiling after their interaction.