If you see “Beautiful Creatures” star Emmy Rossum muttering to herself, she’s just practicing lines. “I’ll be walking down the street saying words, practicing, and people think I’m crazy,” she told us at Cole’s Greenwich Village. “So when I see people talking to themselves, I never know if they’re schizophrenics or actors.” Rossum, who plays a witch in her new film, further told us she’d choose “invisibility,” if she could have a magical power, to “spy on ex-boyfriends . . . But that’s what Facebook is for.”