Hi Jonathan,
I help SEOs all day long that broke the rules and got caught and their client pays the price. Some fight for months to get their listing back, so I am a bit of a purist about the rules because I know the damage breaking them can do.
UPS or Pak Mail type addresses are prohibited and not considered by Google a "real" business location. Does not matter if she meets clients there.
Here is Google's thinking. (And I work with upper management with Google on a daily basis on cases like this, so I know for a fact.) If someone found her on a map, drove across town, walked into the Pak Mail would she be there?
Also does not matter if address is hidden. Google still sees address in dashboard. They can find out it's at Pak Mail just like I did (http://goo.gl/maps/Ikmu3) and then the listing is toast as mailing addresses are not allowed period.
Does not matter if people online that claim to be experts SAY it's OK to do add city or KW to name or if competitors show their address.
It's like if I told you "it's OK to park in that no parking zone - I do it all the time!"
IF YOU are the UNLUCKY ONE to get CAUGHT - neither the cop or Google will accept the excuse that "others do it and get away with it" OR "some blogger told me it was OK to do it."
Photogs are under high scrutiny so sometimes Google does an industry sweep of a city looking for violations. IF they catch that mailing address or KW stuffed name, you could be in trouble. And if they catch the competitors showing their address, they could be too.