Closed days, handled
Add a closure with the first and last day you are closed and, if you like, what she should say, such as the day you are back or a number for emergencies. On those days she tells callers you are closed, gives them the day you open again and offers no bookings.
Notices with an end date
Some things callers only need to hear for a while: "fully booked until Friday, but we can take your details for a cancellation", or "we have moved to a new workshop round the corner". Add a notice, choose the day it stops, and she passes it on.
Mentioned when it matters
She does not read every notice out on every call. She brings one up when the caller asks about a date it covers, wants to book or call in, or you are closed for it. She knows about closures in the next six weeks, so callers asking about those days hear the right answer before they arrive.
The real reopening day
When she gives your next opening time she skips your closed days, so callers hear the day you are actually back, not the day you would normally open.
Nothing to switch back
Closures and notices stop by themselves after their last day. On closed days she answers as she does out of hours, so callers can still leave a message.