While Sabé's name wasn't even mentioned in TPM, she is mentioned in several SW books that have been released. Here are a few excerpts.
From the Episode I Visual Dictionary:
The most important handmaiden is Sabé. First in line to become the royal decoy in times of danger, she dresses as the Queen and hides her features with white makeup. Amidala has coached Sabé in regal bearing and speech. Even so, she plays the role with apprehension, concerned that a subtle slip will give her sovereign away.
From Queen Amidala's Journal:
I've called one of my handmaidens to my chambers. Her name is Sabé. She is exactly my height and has brown eyes, like me.
She's the perfect decoy.
Sabé is the bravest and cleverest of all my attendants. She is also my best friend.
"It's time," I told her. "I have to ask of you something I have no right to ask. Posing as Queen will put you in grave danger."
She didn't flinch. She took one look out the window, at the battle droids ringing the square.
"I am ready for whatever happens, Your Highness," she said quietly.
"Padmé," I corrected softly. We exchanged sad smiles.
We barely had time to paint her face white and her lips crimson. I brought out an impressive cloak with black feathers and Sabé slipped it on. Perfect.
Then I slipped off the amulet I always wear around my neck. My parents gave it to me when I left to take on the Governorship of Theed. It's a stone my father found on our land. My mother fashioned the clasp.
The amulet means everything to me. All the love and protection my parents gave to me is concentrated into that smooth stone. I told Sabé to wear it.
Sabé took a step back, already shaking her head. She knew what the amulet meant to me. But I insisted.
"Take it," I said. "It's all I have to give."
I pray it will protect her. I'll wear it again when Naboo is free.
Now that I am Padmé, the Queen can command me to perform tasks. I told Sabé she must do this, or it will look suspicious. But does Sabé get just a little pleasure out of telling me to clean up an astromech droid?
Maybe. She's only human.
I had to wait until we reached Palpatine's Senatorial quarters to switch places with Sabé. Here, no one will notice if Padmé disappears. And Sabé will shroud herself and fade into the background.
As Sabé and I changed places, I thanked her for her courage and skill.
"We all need courage now. You most of all," Sabé answered and pressed my hand. There is a fierceness to her quiet ways. Her touch was gentle, but her eyes blazed. "I know you will see us through this, Queen Amidala."
Her faith gave me courage.
I know that Sabé is glad to help. But I sensed her relief when she donned her handmaiden's cloak again.