Rune Factory 3 Question

Sorry if the answer is obvious, I just don't know. Well, for some strange reason, I started playing Rune Factory 3 late and as I woke up (Fall 10, I think), Sakuya walked in my house LIKE A BOSS for no reason. After a few hours, she left.
Why?

She can buy stuff from you box in the field thing

Replying to #2

Really?
OH NO SHE DIDN'T