She thinks she knows why Ben gave Luke to her and Owen. She thinks that he was scared for the fate of the boy if he lived with him; he must fear that he will be hunted down and killed by the Empire.
(But Jedi are not supposed to be scared, are they?)
Thats what she hears anyway.
Perhaps, she thinks, that he also wanted Luke to have a relatively normal childhood rather than living with a man who is now widely held as an outcast.
Yes, she thinks, that must be it.