Do your provider offer extras ?Only thing I can think of that she does not offer that but will let someone else.
I had a similar experience at a place near Lakewood NJ a few years ago. Arrived kind of early around 12:30 one Sunday afternoon. Received a nice TM before returning to the room and a 10-15 massage. Provider was not bad to look at but I remember thinking how plain / conservative she was dressed. She whispered "you want boom?" and when I nodded yes she said "okay I send girl". in walked another attractive woman who was more dressed for the roll. Did the job and she got the whole tip for 25 minutes of effort. On the way out I slipped another 20 to the first one and wished her well.
I always assumed that i was the early entry and the owner didn't want the business to walk out the door so she held down the fort until the talent arrived.
Now that I think about it, there was another two instances at a place called 209 on 11th in Philly (near Thai Beauty). Towards the end of their reign there was a 50 ish dude behind the counter who would send you to the sauna. Then like 10 minutes later a provider would walk in the front door, full coat and get to business. I got the feeling that he was flipping the place (it's now a small hotel, I think) but he didn't want easy money walking out the door so he allowed a little hanky panky in the unused rooms. I saw this on two occasions. The girls didn't show any respect for him and I got the feeling that they left their apartment and stopped over for the quick hit and money. Who knows, could have been his wife or her friends?