The landlord, provided she provided adequate notice, typically 24 hours in advance, can do a walk-through for several reasons.
See http://www.tenant.net/Other_Areas/Calif/misc/nffland.html about when landlord may enter.
The walk through can be a move-in/move-out inspection to make sure the property is in the same condition as when she rented to you.
She can also check it out to discern if there are any repairs that need to be done, and to determine who is responsible for repairs, as well as get estimates.
The walk-through may also be to honor her obligation if there is already a buyer, and the transaction is about to close. The buyer has a right to do the walk-through to make sure the property is in the same condition as when they buyer saw it.
But in both cases, the walk through should be on the date that was agreed upon between you and the landlord. If there's a change, then she will need to give you adequate notice for the change.