If I really thought she was trafficked I wouldn't go through with the meet. I don't know what I would do though with regards to money. On one hand she should get it, on the other hand would she even get to keep the money? Would I inform the police? I would like to think that I would.
I have never been in that situation, thus some of the reasons for the post to begin with.
I have a fair bit of punting experience, but the part of the world I was in the girls were not trafficked, they were feeding their families back home. In many cases the view point of the girls was that they were doing me a favour so i was doing them a favour, it still amounted to prostitution but they didnt look at it that way.