Why do you believe Mrs. Jones was so kind to the boy who tried to steal her purse?

Though she comes across as quite a stern, no-nonsense kind of a person, Mrs. Jones defies our expectations by showing great kindness to Roger. The boy has just tried to steal her purse, but instead of marching him off to the nearest police station, she takes him home, cleans him up, and gets him something to eat.
Mrs. Jones has a lot of life experience, and in her time, she's doubtless come across many youngsters caught up in criminality. But over the years she'll have also come to know the difference between hardcore criminals and those, like Roger, who appear to have been driven to crime purely out of desperation. Just one look at Roger, with his dirty face and his hungered appearance, tells Mrs. Jones that this is a vulnerable child who needs help, not punishment.
At the same time, Mrs. Jones has no intention of interfering in what she gathers is Roger's troubled home life. When she gives the boy $10 it's in the hope—rather than the expectation—that he'll put the money to good use. Mrs. Jones is wise enough to know that Roger's unlikely to change suddenly because someone's just given him some money, but at least she can say that she's tried to set him on the right path in life. What Roger chooses to do with that life is entirely up to him.