If it was Kimber James or Allanah Starr, I might. That's really one of those questions that I don't know what I'd do unless I was actually there. If I found out it was a shemale after it started to get hot, then I don't know if I'd be able to stop.
Having her do me, though, I wouldn't do. If she wants to look like/be a girl, then she gets the sex like a girl.