The manner in which Terezi lets out a shriek of humorous dismay makes it clear that Albert's assumptions were right. She is extremely ticklish, and she squirms violently, trying to pull out of his grasp and away from his tickling.

"Traitor! Fiend! Betrayal! Stop, stop, stop!" She continues to shriek and squirm, making a ridiculous amount of noise for after curfew hours.