Do girls repeat in the calendar?
I mean:

1. Can the same show randomly repeat within 2 weeks to double in the calendar?
2. Can it ever repeat before all show have already appeared one time each (like the "used" trailer strikes out from the random list)?

What experience did you have?

As far as I know, it can't repeat within the three weeks unless you have all (or nearly all) the girls so it can't find a girl you haven't got.

Once you've downloaded a girl, she doesn't repeat unless you've downloaded (almost) all the girls as above. And as long as you leave a couple of girls undownloaded at the end of every Monday, those repeat girls will get replaced with the current week's new girls.

If you don't download, then once she falls out of the calendar, theoretically the girl is available for putting in immediately, but the odds are pretty low given the calendar only includes 21/250+ girls at a time.