The principal place of business is where you perform the tasks that earn you money. She does not perform the babysitting in her home and taking an appointment from her home does not make her home her place of business.
An Uber driver starts their day when they arrive at their first pickup point. Then all of their mileage counts until their final person is dropped off and they return home. The home is not their place of business. The IRS has never paid for a commute from you home to your work, no matter how far you have to drive to get to work.
