How does Aunt Rachel let Kit know that she knows about her visits to Hannah?

From the text:

"Where are you going. Kit?"
Kit looked down, not answering.
Her aunt studied her. "Wait," she said then. She went into the kitchen and came back after a moment with a small package
which she held out to Kit shamefacedly.
It was a bit of leftover apple tart. So Aunt Rachel had known all the time! Kit suddenly threw her arms about her aunt.
"Oh, Aunt Rachel--you are so good!"
"I can't help it, Kit," her aunt said worriedly. "I don't approve at all. But I can't bear to think of any- one going hungry when we have such plenty."