Why did Turtle say she didn't feel so good after she called Angela at the hospital?

Turtle felt sick because she thought her sister would be found out.

Turtle hung up the phone. If Theo knew, others knew. Angela had set off those fireworks wanting to get caught, but it was different now. Now she was confused, now she was just plain scared. They could force a confession out of her in no time, the guilt was right there staring out of those big blue eyes. Maybe they’re questioning her now. “Baba, I’m not feeling so good; I think I’ll go home to bed.”