Fantine has taken a liking to watching people. She doesn't keep much company, but she hardly feels alone when she is observing others. She likes to make up backstories for those who are particularly eye-catching. Of course she gives them only the most pleasant of lives.
Today it's a young girl. She smiles to herself as she absently thumbs at the fresh stitching in her sleeve -- she'd repaired it only an hour or so earlier.
She tries to guess at the young woman's age, but she's never been especially good at gleaning real details about a person. Instead she relaxes back, allowing herself to entertain her own fantasy.
She decides this girl knows her Cosette; that they are friends and that they meet up every few days. Oh, they must talk about such wonderful things. Happy things, of course, only happy things. Nothing less for her daughter.
So caught up in her own make-believe is she that it hardly seems strange at all to her to call out to the girl. Only afterwards does she realize that she's gotten carried away. She may have been a bit lonelier than she liked to admit, she supposes.
"Pardon me. You looked like -- someone else."