she didn't specificly say this week or next so i don't know.
If it was Friday, I would probably say "I would like you to work tomorrow."
If it was for working the following week, I would say, "I would like you to work next week Saturday." Or Saturday next week.
But yes, if this is a real question about working, ask her to clarify.
I am not a teacher.
If she didn't specify, I would assume it meant the nearest Saturday.