This is your typical tourist area.  Lots of hotels and restaurants are within walking distance.  The weather will be nice when your model visits, she should be able to see the Golden Gate bridge.  Plenty of things to do during down time.  I've seen many a providers there.

You can try  near Union Square, but might be tough or expensive to get a good room.  There is a convention in town this coming week. PCBC ( pacific coast builders convention) used to be big but has taken a hit like most other industries.

I urge your model to stay at one of the Union Square hotels. Union Square is centrally located, very lively, and visitors can arrive easily by the Metro. There are cabs everywhere. Cab Stands are present at the larger hotels. Your model can find many decent restaurants within short walking distance--some good ones are in the hotels. As a resident of SF, it is the most convenient and most discrete place for me to visit a model. 83% of the grand hotels in the City are located in Union Square. So for many reasons, I'd go with the Union Square. I recommend especially the St Francis Westin Hotel.

Best wishes,