Angel is definitely the baby bird of the flock. For one, Max sees her that way and has some serious maternal feelings toward her:
I'd never told the others, but I just loved, loved, loved Angel. Maybe because I'd been taking care of her practically since she was a baby. Maybe because she was so incredibly sweet and loving herself.
"Maybe because I'm like your little girl," said Angel, turning around to look at me. (3.25-26)
But just because Angel is everyone's baby and is coddled by the rest of the flock members, doesn't mean that she's your average little girl. She's got some incredible powers and can both read and influence other peoples' thoughts. This makes her one of the more powerful hybrids in the book, even though so far she's just using her powers for things like forcing strangers to buy teddy bears for her. It's just a hunch, but we're thinking Angel's someone to watch out for later in the series.