I was told to err on the side of caution - maybe two weeks and see if your cat seems settled. If you think she might wander, establish a 'dinnertime' routine wach day of the two weeks. When her food is ready, tap her dish so she can hear it. When it's time to let her out, make it her meal time, and then stand at the door and tap her dish, she'll come back for her food. A couple of days of this, and she should have got her bearings, and you can let her out when she wants to go.