How did the Female Titan manage to get out of her titan form and escape while surrounded by a horde of titans?

Question

In episode 20 of the anime, when Annie, as the Female Titan, falls into Erwin's trap and is restrained, she calls over a horde of titans to devour her titan body. Her titan body is shown to be torn apart and eaten as the titans surround her.

She is next seen in her human form, hiding herself among other people in the squad. When her cover was blown, she turns into her titan form for the second time and eliminates the League of Legends, as seen in episode 21.

How did Annie Leonhart manage to get out of her titan form and escape from the scene, all while surrounded by a horde of titans?

Answer 1

You may have missed this, but it was actually explained near the end of the episode.

Whilst riding on horseback

Zoe: Erwin, why did you order Levi to resupply? There's no time to waste.

Erwin: The female-form Titan was eaten. But did you see the person inside get eaten? I didn't.

Zoe: You can't mean...

Erwin: Ah, yes. If your original hypothesis was correct, they can still move to a degree after regaining human form. If they'd prepared 3D Maneuver Gear in advance...

Major spoiler for those who have not finished watching Attack on Titans

After this we see (unbeknownst to the audience yet), Annie zooming through the trees using already prepared 3D Maneuver Gear

Then we head back to Erwin talking again...

Erwin: The person inside the female-form titan is wearing our uniform right now... The enemy is now camouflaged as one of the troops.

Annie was able to escape her titan form because you can still move to a degree even after regaining human form, which would explain why she was able to escape before getting eaten herself.